entranceConnecting sas drives to the controller. Difference between SAS and SATA
Over the past two years, few changes have accumulated:
- Supermicro is ditching the proprietary "flipped" UIO form factor for controllers. Details will be below.
- LSI 2108 (SAS2 RAID with 512MB cache) and LSI 2008 (SAS2 HBA with optional RAID support) are still in service. The products on these chips, both from LSI and from OEM partners, are fairly well debugged and still relevant.
- LSI 2208 appeared (the same SAS2 RAID with LSI MegaRAID stack, only with a dual-core processor and 1024MB cache) and (an improved version of LSI 2008 with a faster processor and PCI-E 3.0 support).
Moving from UIO to WIO
As you remember, UIO cards are ordinary PCI-E x8 cards, in which the entire element base is located on the back side, i.e. when installed in the left riser is on top. It took such a form factor to install the cards in the lowest slot of the server, which allowed four cards to be placed in the left riser. UIO is not only a form factor for expansion cards, it is also cases designed for installing risers, the risers themselves and motherboards of a special form factor, with a cutout for the lower expansion slot and slots for installing risers.This solution had two problems. First, the non-standard form factor of the expansion cards limited the choice of the client. under the UIO form factor, there are only a few SAS, InfiniBand and Ehternet controllers. Secondly, there is an insufficient number of PCI-E lanes in the slots for risers - only 36, of which only 24 lanes for the left riser, which is clearly not enough for four motherboards with PCI-E x8.
What is WIO? At first, it turned out that it was possible to place four boards in the left riser without the need to "turn the sandwich butter up", and risers for ordinary boards appeared (RSC-R2UU-A4E8 +). Then the problem of the lack of lines (now there are 80) was solved by using slots with a higher density of contacts.
| UIO riser RSC-R2UU-UA3E8 + |
 |
| WIO riser RSC-R2UW-4E8 |
Results:
- WIO risers cannot be installed on UIO motherboards (such as X8DTU-F).
- UIO risers cannot be installed in new cards that are WIO-compliant.
- There are risers for WIO (on the motherboard) that have a UIO slot for cards. In case you still have UIO controllers. They are used in platforms for Socket B2 (6027B-URF, 1027B-URF, 6017B-URF).
- There will be no new controllers in the UIO form factor. For example, the USAS2LP-H8iR controller on the LSI 2108 chip will be the last one, there will be no LSI 2208 under UIO - just a regular MD2 with PCI-E x8.
PCI-E controllers
At the moment, three types are relevant: RAID controllers based on LSI 2108/2208 and HBA based on LSI 2308. There is also a mysterious SAS2 HBA AOC-SAS2LP-MV8 on a Marvel 9480 chip, but write about it because of its exoticism. Most use cases for internal SAS HBAs are ZFS storage under FreeBSD and various Solaris flavors. Due to the absence of support problems in these operating systems, the choice falls on LSI 2008/2308 in 100% of cases.LSI 2108
In addition to the UIO "shny AOC-USAS2LP-H8iR, which is mentioned in the addition, two more controllers have been added:
LSI 2108, SAS2 RAID 0/1/5/6/10/50/60, 512MB cache, 8 internal ports (2 SFF-8087 connectors). It is an analogue of the LSI 9260-8i controller, but manufactured by Supermicro, there are minor differences in the board layout, the price is $ 40-50 lower than LSI. All additional LSI options are supported: activation, FastPath and CacheCade 2.0, battery protection of the cache - LSIiBBU07 and LSIiBBU08 (now BBU08 is preferred, it has an expanded temperature range and includes a cable for remote mounting).
Despite the introduction of more efficient controllers based on the LSI 2208, the LSI 2108 is still relevant due to the price reduction. Performance with conventional HDDs is enough in any scenario, the IOPS limit for working with SSDs is 150,000, which is more than enough for most budget solutions.
LSI 2108, SAS2 RAID 0/1/5/6/10/50/60, 512MB cache, 4 internal + 4 external ports. Analogous to the LSI 9280-4i4e controller. Convenient for use in expander bodies, because there is no need to bring the output from the expander outside to connect additional JBODs, or in 1U enclosures for 4 disks, if necessary, to provide the ability to expand the number of disks.Supports the same BBU and activation keys.
LSI 2208
LSI 2208, SAS2 RAID 0/1/5/6/10/50/60, 1024MB cache, 8 internal ports (2 SFF-8087 connectors). It is analogous to the LSI 9271-8i controller. LSI 2208 is further development LSI 2108. The processor has become a dual-core, which allowed raising the IOPS performance limit as much as 465000. Added support for PCI-E 3.0 and increased to 1GB cache.
The controller supports BBU09 cache battery protection and CacheVault flash protection. Supermicro supplies them under the part numbers BTR-0022L-LSI00279 and BTR-0024L-LSI00297, but it is easier to purchase from us through the LSI sales channel (the second part of the part numbers are the native LSI part numbers). MegaRAID Advanced Software Options activation keys are also supported, part numbers: AOC-SAS2-FSPT-ESW (FastPath) and AOCCHCD-PRO2-KEY (CacheCade Pro 2.0).
LSI 2308 (HBA)
LSI 2308, SAS2 HBA (with IR firmware - RAID 0/1 / 1E), 8 internal ports (2 SFF-8087 connectors). This is the same controller, comes with different firmware. AOC-S2308L-L8e - IT firmware (pure HBA), AOC-S2308L-L8i - IR firmware (with RAID 0/1 / 1E support). The difference is that L8i can work with IR and IT firmware, L8e - only with IT, IR firmware is blocked. Analogous to the LSI 9207-8 controller i... Differences from LSI 2008: faster chip (800 MHz, as a result - IOPS limit increased to 650 thousand), PCI-E 3.0 support appeared. Application: software RAID "s (ZFS, for example), budget servers.
On the basis of this chip, there will be no cheap controllers with support for RAID-5 (iMR stack, from ready-made controllers - LSI 9240).
Onboard controllers
In the latest products (X9 boards and platforms with them), Supermicro denotes the presence of a SAS2 controller from LSI with the number "7" in the part number, and the number "3" for the chipset SAS (Intel C600). However, no distinction is made between LSI 2208 and 2308, so be careful when choosing a board.- The LSI 2208-based controller soldered on the motherboards has a maximum of 16 disks. When adding 17, it simply will not be detected, and in the MSM log you will see the message "PD is not supported". This is compensated for by a significantly lower price. For example, a bundle "X9DRHi-F + external controller LSI 9271-8i" will cost about $ 500 more than X9DRH-7F with LSI 2008 on board. It is not possible to bypass this limitation by flashing it into the LSI 9271 - flashing another SBR block, as in the case of the LSI 2108, does not help.
- Another feature is the lack of support for CacheVault modules, the boards simply lack space for a special connector, so only BBU09 is supported. The possibility of installing the BBU09 depends on the enclosure used. For example, LSI 2208 is used in 7127R-S6 blade servers, there is a BBU connector there, but to mount the module itself, you need an additional MCP-640-00068-0N Battery Holder Bracket.
- SAS HBA (LSI 2308) firmware will be needed now, because in DOS on any of the boards with LSI 2308 sas2flash.exe does not start with the error "Failed to initialize PAL".
Controllers in Twin and FatTwin platforms
Some 2U Twin 2 platforms are available in three versions, with three kinds of controllers. For example:- 2027TR-HTRF + - Chipset SATA
- 2027TR-H70RF + - LSI 2008
- 2027TR-H71RF + - LSI 2108
- 2027TR-H72RF + - LSI 2208
| BPN-ADP-SAS2-H6IR (LSI 2108) |
 |
| BPN-ADP-S2208L-H6iR (LSI 2208) |
| BPN-ADP-SAS2-L6i (LSI 2008) |
Supermicro xxxBE16 / xxxBE26 cases
Another topic that is directly related to controllers is the modernization of cases with. There are varieties with an additional cage for two 2.5 "drives located on the rear panel of the case. Purpose - a dedicated disk (or mirror) for system boot. Of course, the system can be loaded by allocating a small volume from another disk group or from additional disks fixed inside the case (in 846 cases, you can install additional fasteners for one 3.5 "or two 2.5" drives), but the updated modifications are much more convenient:
Moreover, these additional disks do not have to be connected to the chipset SATA controller. Using the SFF8087-> 4xSATA cable, you can connect to the main SAS controller through the SAS expander output.
P.S. Hope the information was helpful. Do not forget that the most complete information and technical support for Supermicro, LSI, Adaptec by PMC and other vendors, contact True System.
SAS (Serial Attached SCSI) is a serial computer interface designed to connect a variety of storage devices such as tape drives. SAS is designed to replace the parallel SCSI interface and uses the same SCSI command set.
SAS is backward compatible with SATA interface: SATA II and SATA 6 Gb / s devices can be connected to a SAS controller, but SAS devices cannot be connected to a SATA controller. The latest SAS implementation provides data transfer rates up to 12Gbps per line. 24Gb / s SAS specification expected by 2017
SAS combines the advantages of SCSI (deep command queue sorting, good scalability, high noise immunity, long maximum cable length) and Serial ATA (thin, flexible cheap cables, hot-plugging, point-to-point topology, allowing you to achieve better performance in complex configurations) with new unique capabilities - such as an advanced connection topology using hubs called SAS expanders (SAS expanders), connecting two SAS channels to one (both to increase reliability and performance), work on one disk as with SAS and SATA interface.
In combination with the new addressing system, this allows you to connect up to 128 devices per port and have up to 16256 devices on the controller, without the need for any manipulation of jumpers, etc. The limitation of 2 Terabytes on the volume of the logical device has been removed.
The maximum cable length between two SAS devices is 10 m when using passive copper cables.
Actually, the SAS data transfer protocol means three protocols at once - SSP (Serial SCSI Protocol), which provides the transfer of SCSI commands, SMP (SCSI Management Protocol), which works with SCSI control commands and is responsible, for example, for interacting with SAS expanders, and STP (SATA Tunneled Protocol), which implements support for SATA devices.
The currently produced ones have internal SFF-8643 connectors (it can also be called mini SAS HD), but there may still be SFF-8087 (mini SAS) connectors, to which 4 SAS channels are output.
The external version of the interface uses the SFF-8644 connector, but the SFF-8088 connector may still be encountered. It also supports four SAS channels.
SAS controllers are fully compatible with SATA drives and SATA baskets / backplanes- connection is usually carried out using cables:. The cable looks something like this:
SFF-8643 -> 4 x SAS / SATA
Usually SAS cages / backplane (backplane) have SATA connectors on the outside and you can always insert regular SATA drives into them, therefore they (such cages) are usually called SAS / SATA.
However, there are reversible versions of such a cable for connecting a backplane with internal SFF-8087 connectors to a SAS controller that has regular SATA connectors. Such cables are not interchangeable with each other.
SAS drives cannot be connected to a SATA controller or installed in a SATA cage / backplane.
To connect SAS disks to a controller with SFF-8643 or SFF-8087 internal connectors without using SAS baskets, you must use a SFF-8643-> SFF-8482 or SFF-8087-> SFF-8482 cable, respectively.
The existing versions of the SAS interface (1.0, 2.0, and 3.0) are compatible with each other, that is, a SAS2.0 disk can be connected to a SAS 3.0 controller and vice versa. In addition, the upcoming 24 Gb / s version will also be backward compatible.
SAS connector types
| Image | Codename | Also known as | External/ interior |
Number of contacts | Number of devices |
With the advent of a sufficiently large number of Serial Attached SCSI (SAS) peripherals, we can state the beginning of the transition of the corporate environment to the rails of new technology. But SAS is not only the established successor to UltraSCSI technology, but it is also realizing new uses, taking the scalability of systems to unimaginable heights. We decided to demonstrate the potential of SAS by taking a close look at the technology, host adapters, hard drives, and storage systems.
SAS cannot be called completely new technology: she takes the best of both worlds. The first part of SAS is about serial communication, which requires fewer physical wires and pins. The shift from parallel to serial transmission also eliminated the bus. Although according to current SAS specifications throughput Defined at 300 MB / s per port, which is less than 320 MB / s for UltraSCSI, replacing the shared bus with a point-to-point connection is a significant advantage. The second part of SAS is the SCSI protocol, which remains powerful and popular.
SAS can use and large set RAID varieties... Giants such as Adaptec or LSI Logic offer advanced features for expansion, migration, socketing and other capabilities in their products, including those related to distributed RAID arrays across multiple controllers and drives.
Finally, most of the actions mentioned today are performed on the fly. Here we should highlight the excellent products AMCC / 3Ware , Areca and Broadcom / Raidcore allowing enterprise-class functionality to be migrated to SATA spaces.
Compared to SATA, the traditional SCSI implementation is losing ground on all fronts except for high-end enterprise solutions. SATA offers suitable hard drives, has a good price and a wide range of decisions... And let's not forget another "smart" SAS feature: it fits easily with existing SATA infrastructures because SAS host adapters work seamlessly with SATA drives. But you won't be able to connect a SAS drive to a SATA adapter.
Source: Adaptec.
First, it seems to us, we should turn to the history of SAS. The SCSI standard (stands for "small computer system interface") has always been considered as a professional bus for connecting drives and some other devices to computers. Hard drives for servers and workstations continue to use SCSI technology. Unlike the mainstream ATA standard, which only allows two drives to be connected to a single port, SCSI allows up to 15 devices to be connected on a single bus and offers a powerful command protocol. Devices must have a unique SCSI ID, which can be assigned either manually or via SCAM (SCSI Configuration Automatically). Because device IDs for buses on two or more SCSI adapters may not be unique, Logical Unit Numbers (LUNs) have been added to help identify devices in complex SCSI environments.
SCSI hardware is more flexible and reliable than ATA (also called IDE, Integrated Drive Electronics). Devices can be connected both inside the computer and outside, and the cable length can be up to 12 m, if only it is correctly terminated (in order to avoid signal reflections). With the evolution of SCSI, numerous standards have emerged that stipulate different bus widths, clock speeds, connectors and signal voltages (Fast, Wide, Ultra, Ultra Wide, Ultra2, Ultra2 Wide, Ultra3, Ultra320 SCSI). Fortunately, they all use the same set of commands.
Any SCSI communication is established between the initiator (host adapter) sending commands and the target drive responding to them. Immediately after receiving a set of commands, the target drive sends a so-called sense-code (status: busy, error, or free), by which the initiator knows whether he will receive the desired response or not.
The SCSI protocol specifies almost 60 different commands. They are divided into four categories: non-data, bi-directional, read data, and write data.
The limitations of SCSI start to show up when you add drives to the bus. Today, you can hardly find a hard drive capable of fully utilizing the 320MB / s bandwidth of the Ultra320 SCSI. But five or more drives on a single bus is another matter entirely. An option would be to add a second host adapter for load balancing, but it comes at a cost. The problem with cables too: Twisted 80-wire cables are very expensive. If you also want to get "hot-swap" drives, that is, easy replacement of a failed drive, then you need special equipment (backplane).
Of course, it is best to place the drives in separate rigs or modules, which are usually hot-swappable, along with other nice control features. As a result, there are more number professional SCSI solutions. But they all cost a lot, which is why the SATA standard has developed so rapidly in recent years. While SATA will never meet the needs of high-end enterprise systems, it complements SAS perfectly to create scalable new solutions for next-generation networking environments.
SAS does not share a bus across multiple devices. Source: Adaptec.
SATA
On the left is the SATA connector for data transfer. On the right is the power supply connector. There are enough pins to supply 3.3V, 5V and 12V to each SATA drive.
The SATA standard has been on the market for several years, and today it has reached its second generation. SATA I featured 1.5 Gbps throughput with two serial connections using low-voltage differential signaling. The physical layer uses 8/10 bit coding (10 actual bits for 8 data bits), which explains the maximum interface bandwidth of 150 MB / s. After the transition of SATA to a speed of 300 MB / s, many began to call new standard SATA II, although with standardization SATA-IO(International Organization) planned to add more features first, and then call it SATA II. Hence the latest specification is called SATA 2.5, it includes SATA extensions such as Native Command Queuing(NCQ) and eSATA (external SATA), port multipliers (up to four drives per port), etc. But additional functions SATA is optional for both the controller and the hard drive itself.
Let's hope that in 2007 SATA III at 600 MB / s will still be released.
While parallel ATA (UltraATA) cables were limited to 46cm, then SATA cables can be up to 1m long, and for eSATA they can be twice as long. Instead of 40 or 80 wires, serial transmission requires only a single pins. Therefore, SATA cables are very narrow, easy to run inside the computer case, and do not interfere with airflow as much. The SATA port relies on one device, which allows this interface to be classified as point-to-point.
SATA connectors for data and power are provided with separate plugs.
SAS
The signaling protocol is the same as that of SATA. Source: Adaptec.
A nice feature of Serial Attached SCSI is that the technology supports both SCSI and SATA, as a result of which you can connect SAS or SATA drives (or both) to SAS controllers. However, SAS drives cannot work with SATA controllers due to the Serial SCSI Protocol (SSP). Like SATA, SAS follows a point-to-point connection for drives (300MB / s today), and thanks to SAS expanders (or expanders), more drives can be connected than the available SAS ports. SAS hard drives support two ports, each with its own unique SAS ID, so you can use two physical connections to provide redundancy by connecting the drive to two different hosts. Thanks to the STP (SATA Tunneling Protocol) SAS controllers can communicate with SATA drives connected to the expander.
Source: Adaptec.
Source: Adaptec.
Source: Adaptec.
Of course, the only physical connection of the SAS expander to the host controller can be considered " bottleneck", so the standard provides for wide (wide) SAS ports. A wide port groups multiple SAS connections into a single link between any two SAS devices (usually between a host controller and an expander / expander). The number of connections within a link can be increased, it depends on However, redundant connections are not supported, and any loops or rings must not be allowed.
Source: Adaptec.
Future SAS implementations will add 600 and 1200 MB / s bandwidth per port. Of course, the performance of hard drives will not increase in the same proportion, but it will be more convenient to use expanders on a small number of ports.
Devices named "Fan Out" and "Edge" are expanders. But only the main Fan Out expander can work with the SAS domain (see 4x link in the center of the diagram). Up to 128 physical connections are allowed per Edge expander, and wide ports can be used and / or other expanders / drives can be connected. Topology can be quite complex, yet flexible and powerful at the same time. Source: Adaptec.
Source: Adaptec.
The backplane is the basic building block of any storage system that needs to be hot-pluggable. Therefore, SAS expanders often include powerful rigs (either in a single package or not). Typically a single link is used to connect a simple snap-in to the host adapter. Expanders with built-in snap-ins, of course, rely on multichannel connections.
There are three types of cables and connectors designed for SAS. SFF-8484 is a multicore internal cable that connects the host adapter to the rig. In principle, the same can be achieved by splitting this cable at one end into several separate SAS connectors (see illustration below). SFF-8482 is the connector that connects the drive to a single SAS interface. Finally, the SFF-8470 is an external multicore cable, up to six meters long.
Source: Adaptec.
SFF-8470 cable for external SAS multichannel connections.
Stranded cable SFF-8484. Four SAS channels / ports pass through one connector.
SFF-8484 cable allowing connection of four SATA drives.
SAS as part of SAN solutions
Why do we need all this information? Most users won't even come close to the SAS topology we discussed above. But SAS is more than a next-generation interface for professional hard drives, although it is ideal for building simple and complex RAID arrays based on one or more RAID controllers. SAS can do more. This is a point-to-point serial interface that scales easily as you add the number of links between any two SAS devices. SAS drives come with two ports, so you can connect one port through an expander to a host system, and then create a backup path to another host system (or another expander).
The communication between SAS adapters and expanders (as well as between two expanders) can be as wide as the number of SAS ports available. Expanders are usually rack systems that can accommodate a large number of drives, and possible connection SAS to an upstream device in the hierarchy (for example, a host controller) is limited only by the capabilities of the expander.
With a rich and functional infrastructure, SAS allows you to create complex storage topologies, rather than dedicated hard drives or separate network storage. In this case, "complex" does not mean that it is difficult to work with such a topology. SAS configurations consist of simple disk snap-ins or use expanders. Any SAS link can be expanded or narrowed, depending on the bandwidth requirements. You can use both powerful SAS hard drives and large SATA models. Together with powerful RAID controllers, you can easily configure, expand or reconfigure data arrays - both in terms of RAID level and from the hardware side.
All of this becomes all the more important when you consider how quickly corporate storage is growing. Today everyone is talking about a SAN - a storage area network. It implies a decentralized organization of the storage subsystem with traditional servers, using physically remote storage. Over existing gigabit Ethernet or Fiber Channel networks, a slightly modified SCSI protocol is launched, encapsulated in Ethernet packets (iSCSI - Internet SCSI). A system that runs from a single hard drive to complex nested RAID arrays becomes a so-called target and is tied to an initiator (host system, initiator), which treats the target as if it were just a physical element.
iSCSI, of course, allows you to create a strategy for storage development, data organization or access control. We gain another level of flexibility by removing direct attached storage, allowing any storage subsystem to become an iSCSI target. Moving to off-site storage makes the system independent of storage servers (critical point of failure) and improves hardware manageability. From a software point of view, the storage is still "inside" the server. The iSCSI target and initiator can be located nearby, on different floors, in different rooms or buildings - it all depends on the quality and speed of the IP connection between them. From this point of view, it is important to note that SAN is poorly suited to operational requirements. available applications like databases.
2.5 "SAS hard drives
2.5 "hard drives for the professional world are still considered new. We've been looking at the first such drive from Seagate for quite some time now - 2.5 "Ultra320 Savvio which left a good impression. All 2.5 "SCSI drives use 10,000 rpm spindle speeds, but they do not match the performance level of 3.5" drives at the same spindle speed. The fact is that the outer tracks of the 3.5 "models rotate at a higher linear speed, which provides a higher data transfer rate.
The advantage of small hard drives is not in their capacity: today they still have a maximum of 73 GB, while we get 300 GB for 3.5 "enterprise-class hard drives. In many areas, the ratio of performance to physical volume is very important. or energy efficiency. The more hard drives you use, the more performance you reap - paired with the appropriate infrastructure, of course. And 2.5 "drives consume almost half the power of 3.5" competitors. performance per watt (I / O operations per watt), the 2.5 "form factor gives very good results.
If capacity is your primary concern, 3.5 "10,000 RPM drives are unlikely to be the best choice. The fact is that 3.5" SATA drives provide 66% more capacity (500 instead of 300 GB for hard drive) while keeping the performance level acceptable. Many hard drive manufacturers offer SATA models for 24/7 operation, and the price of drives has been reduced to a minimum. Reliability problems can be solved by purchasing spare drives for immediate replacement in the array.
The MAY line represents Fujitsu's current generation of 2.5 "professional drives. Rotational speeds of 10,025 rpm, 36.7 GB and 73.5 GB capacities. All drives come with 8 MB cache and average read seek times. 4.0 ms and 4.5 ms writes As we have already mentioned, a nice feature of 2.5 "hard drives is the reduced power consumption. Typically, one 2.5 "hard drive can save at least 60% energy compared to a 3.5" drive.
3.5 "SAS hard drives
Underneath the MAX is Fujitsu's current line of high-performance 15,000 RPM hard drives. So the name is quite consistent. Unlike 2.5 "drives, we get a whopping 16MB of cache and a short 3.3ms average seek time for reading and 3.8ms for writing. Fujitsu offers 36.7GB, 73.4GB and 146GB models. GB (with one, two and four platters).
Hydrodynamic bearings have also made their way to enterprise-class hard drives, so the new models run significantly quieter than the previous ones at 15,000 rpm. Of course, these hard drives need to be properly cooled, and the hardware ensures that too.
Hitachi Global Storage Technologies also offers its own line of high-performance solutions. The UltraStar 15K147 runs at 15,000 rpm and has 16 MB cache, just like Fujitsu drives, but the platter configuration is different. The 36.7GB model uses two platters, not one, and the 73.4GB model uses three platters, not two. This indicates a lower data density, but this design, in fact, eliminates the use of the inner, slowest areas of the platters. As a result, the heads have to move less, which gives a better average access time.
Hitachi also offers 36.7GB, 73.4GB, and 147GB models with a timed seek (read) of 3.7ms.
Although Maxtor has already become part of Seagate, the company's product lines are still intact. The manufacturer offers 36, 73 and 147 GB models, all of which differ in spindle speeds of 15,000 rpm and 16 MB cache. The company claims an average seek time of 3.4ms for reads and 3.8ms for writes.
Cheetah has long been associated with high-performance hard drives. A similar association with the release Barracuda Seagate was able to instill in the desktop segment as well, offering the first 7200 rpm desktop drive in 2000.
Available in 36.7 GB, 73.4 GB and 146.8 GB models. They all differ in a spindle speed of 15,000 rpm and a cache of 8 MB. The stated average seek time for reading is 3.5 ms and for writing 4.0 ms.
Host adapters
Unlike SATA controllers, SAS components can only be found on server-grade motherboards or as expansion cards for PCI-X or PCI Express... If we take it a step further and consider the RAID controllers (Redundant Array of Inexpensive Drives), because of their complexity, they are sold, for the most part, in the form of separate cards. RAID cards contain not only the controller itself, but also a chip to accelerate the calculations of redundancy information (XOR engine), as well as cache memory. A small amount of memory is sometimes soldered to the card (most often 128 MB), but some cards allow you to expand the capacity using DIMM or SO-DIMM.
When choosing a host adapter or RAID controller, you should be clear about what you need. The range of new devices is growing just before our eyes. Simple multiport host adapters are comparatively cheap, while powerful RAID cards are expensive. Consider where you will place your drives: for external storage at least one external connector is required. Rack servers usually require low profile cards.
If you need RAID, consider whether you will use hardware acceleration... Some RAID cards consume CPU resources for XORing RAID 5 or 6; others use their own hardware XOR engine. RAID acceleration is recommended for environments where the server does more than store data, such as databases or web servers.
All host adapter cards that we have shown in our article support 300 MB / s per SAS port and allow very flexible implementation of the storage infrastructure. Today, you will hardly surprise anyone with external ports, and consider the support for both SAS and SATA hard drives. All three cards use the PCI-X interface, but PCI Express versions are already in development.
In our article, we paid attention to cards with eight ports, but the number of connected hard drives is not limited to that. With the SAS expander (external), you can connect any storage. As long as a 4-lane connection is sufficient, you can expand the number of hard drives up to 122. Due to the performance cost of calculating the parity information of RAID 5 or RAID 6, typical external RAID storage will not be able to sufficiently load the bandwidth of a 4-lane connection, even with a large number of drives.
The 48300 is a SAS host adapter for the PCI-X bus. The server market continues to be dominated by PCI-X, although more and more motherboards are equipped with PCI Express interfaces.
The Adaptec SAS 48300 uses a PCI-X interface at 133 MHz for 1.06 GB / s bandwidth. Fast enough if the PCI-X bus is not loaded by other devices. If you include a slower device on the bus, then all other PCI-X cards will slow down to the same speed. For this purpose, several PCI-X controllers are sometimes installed on the board.
Adaptec is positioning the SAS 4800 for mid-range, low-end servers and workstations. The MSRP is $ 360, which is quite reasonable. Supports Adaptec HostRAID to migrate to the simplest RAID arrays. In this case, these are RAID levels 0, 1 and 10. The card supports an external four-channel SFF8470 connection, as well as an internal SFF8484 connector paired with a cable for four SAS devices, that is, we get a total of eight ports.
The card fits into a 2U rack server with a low-profile slot cover. The package also includes a CD with a driver, a quick installation guide and an internal SAS cable through which you can connect up to four system drives to the card.
SAS player LSI Logic sent us a SAS3442X PCI-X host adapter, a direct competitor to the Adaptec SAS 48300. It comes with eight SAS ports that are split between two quad-lane interfaces. The heart of the card is the LSI SAS1068 chip. One of the interfaces is intended for internal devices, the second is for external DAS (Direct Attached Storage). The board uses the PCI-X 133 bus interface.
As usual, 300 MB / s is supported for SATA and SAS drives. There are 16 LEDs on the controller board. Eight of them are simple activity LEDs, and eight more are designed to report a system malfunction.
The LSI SAS3442X is a low profile card so it fits easily into any 2U rack server.
Note the driver support for Linux, Netware 5.1 and 6, Windows 2000 and Server 2003 (x64), Windows XP (x64) and Solaris up to 2.10. Unlike Adaptec, LSI has decided not to add support for any RAID modes.
RAID adapters
SAS RAID4800SAS is Adaptec's solution for more complex SAS environments and can be used for application servers, streaming servers, and more. Before us, again, an eight-port card, with one external four-lane SAS connection and two internal four-lane interfaces. But if used external connection, then only one four-channel interface remains from the internal ones.
The card is also designed for PCI-X 133, which provides enough bandwidth for even the most demanding RAID configurations.
As far as RAID modes are concerned, here SAS RAID 4800 easily overtakes its "little brother": RAID levels 0, 1, 10, 5, 50 are supported by default, if you have a sufficient number of drives. Unlike the 48300, Adaptec has included two SAS cables so you can immediately connect eight hard drives to the controller. Unlike the 48300, the card requires a full-length PCI-X slot.
If you decide to upgrade your card to Adaptec Advanced Data Protection Suite then you can upgrade to dual redundant RAID modes (6, 60) and a range of enterprise-class features such as striped mirror drive (RAID 1E), hot spacing (RAID 5EE), and copyback hot spare. Adaptec Storage Manager is a browser-based utility that manages all Adaptec adapters.
Adaptec offers drivers for Windows Server 2003 (and x64), Windows 2000 Server, Windows XP (x64), Novell Netware, Red Hat Enterprise Linux 3 and 4, SuSe Linux Enterprise Server 8 and 9, and FreeBSD.
SAS snap-ins
The 335SAS is a snap-in for four SAS or SATA drives, but must be plugged into a SAS controller. The 120mm fan keeps the drives cool. You will also have to connect two Molex power plugs to the rig.
Adaptec has included an I2C cable that can be used to control tooling through an appropriate controller. But this won't work with SAS drives. An additional LED cable is intended to signal the activity of the drives, but, again, only for SATA drives. The scope of delivery also includes an internal SAS cable for four drives, so an external four-channel cable will be sufficient to connect the drives. If you want to use SATA drives, you will have to use SAS to SATA adapters.
The retail price of $ 369 is not cheap. But you get a solid and reliable solution.
SAS storage
SANbloc S50 is an enterprise grade 12-drive solution. You will receive a 2U rackmount enclosure that connects to SAS controllers. This is one of the best examples of scalable SAS solutions. 12 drives can be either SAS or SATA. Or imagine a mixture of both types. The built-in expander can use one or two 4-lane SAS interfaces to connect the S50 to a host adapter or RAID controller. Since before us is clearly professional solution, it is equipped with two power supplies (redundant).
If you have already purchased an Adaptec SAS host adapter, you can easily connect it to the S50 and use Adaptec Storage Manager to manage your drives. If you install 500 GB SATA hard drives, then we get 6 TB storage. If we take 300 GB SAS drives, then the capacity is 3.6 TB. Since the expander is connected to the host controller with two four-channel interfaces, we get 2.4 GB / s bandwidth, which will be more than enough for any type of array. If you install 12 drives in a RAID0 array, then the maximum throughput is only 1.1 GB / s. In the middle of this year, Adaptec promises to release a slightly modified version with two independent SAS I / O units.
SANbloc S50 contains automatic monitoring and automatic fan speed control. Yes, the device is too loud, so we were relieved to give it away from the lab after the tests were completed. A drive failure message is sent to the controller via SES-2 (SCSI Enclosure Services) or via the I2C physical interface.
Operating temperatures for actuators are 5-55 ° C and for accessories 0-40 ° C.
At the beginning of our tests, we got a peak throughput of just 610 MB / s. By swapping the cable between the S50 and the Adaptec host controller, we were still able to achieve 760 MB / s. We used seven hard drives to load the system in RAID 0 mode. The increase in the number of hard drives did not lead to an increase in throughput.
Test configuration
| System hardware | |
| Processors | 2x Intel Xeon(core Nocona) 3.6 GHz, FSB800, 1 MB L2 cache |
| Platform | Asus NCL-DS (Socket 604) Intel E7520 Chipset, BIOS 1005 |
| Memory | Corsair CM72DD512AR-400 (DDR2-400 ECC, reg.) 2x 512 MB, CL3-3-3-10 |
| System hard drive | Western Digital Caviar WD1200JB 120GB 7200 RPM 8MB Cache UltraATA / 100 |
| Storage controllers | Intel 82801EB UltraATA / 100 Controller (ICH5) Promise SATA 300TX4 Adaptec AIC-7902B Ultra320 Adaptec 48300 8 port PCI-X SAS Adaptec 4800 8 port PCI-X SAS LSI Logic SAS3442X 8 port PCI-X SAS |
| Vaults | 4-bay hot-swappable indoor rig 2U, 12-HDD SAS / SATA JBOD |
| Network | Broadcom BCM5721 Gigabit Ethernet |
| Video card | Built-in ATi RageXL, 8 MB |
| Tests | |
| performance measurement | c "t h2benchw 3.6 |
| Measuring I / O Performance | IOMeter 2003.05.10 Fileserver-Benchmark Webserver-Benchmark Database-Benchmark Workstation-Benchmark |
| System software and drivers | |
| OS | Microsoft Windows Server 2003 Enterprise Edition, Service Pack 1 |
| Platform driver | Intel Chipset Installation Utility 7.0.0.1025 |
| Graphics driver Workstation script. After examining several new SAS hard drives, three associated controllers, and two snap-ins, it became clear that SAS was indeed a promising technology. If you look at the technical documentation of SAS, you will understand why. This is not only the serial SCSI successor (fast, convenient and easy to use), but also an excellent level of infrastructure scalability and scalability that makes Ultra320 SCSI solutions look like a stone age. And the compatibility is just great. If you are planning to purchase professional SATA hardware for your server, then you should take a closer look at SAS. Any SAS controller or hardware is compatible with both SAS and SATA hard drives. Therefore, you can create both high-performance SAS environments and high-capacity SATA environments - or both. Convenient support for external storage is another major benefit of SAS. If SATA storage uses either proprietary solutions or a single SATA / eSATA link, the SAS storage interface allows for increased throughput in groups of four SAS links. As a result, we get the opportunity to increase the bandwidth to meet the needs of applications, and not rest at 320 MB / s UltraSCSI or 300 MB / s SATA. Moreover, SAS expanders allow you to create an entire hierarchy of SAS devices, so that administrators have more freedom of activity. The evolution of SAS devices does not end there. It seems to us that the UltraSCSI interface can be considered outdated and slowly written off. It is unlikely that the industry will improve it, unless it continues to support existing UltraSCSI implementations. All the same, new hard drives, the latest models of storages and accessories, as well as an increase in the interface speed up to 600 MB / s, and then up to 1200 MB / s - all this is intended for SAS. What should be the modern storage infrastructure? The days of UltraSCSI are numbered with the availability of SAS. The sequential version is a logical step forward and copes with all tasks better than its predecessor. The question of choosing between UltraSCSI and SAS becomes obvious. Choosing between SAS or SATA is a little more difficult. But if you look ahead, SAS components are still better. Indeed, for maximum performance or from a scalability perspective, there is no longer an alternative to SAS today. | |
For over 20 years, the parallel bus interface has been the most common communication protocol for most digital storage systems. But with the growing demand for bandwidth and flexibility, the shortcomings of two of the most common parallel interface technologies, SCSI and ATA, have become apparent. The lack of compatibility between parallel SCSI and ATA interfaces — different connectors, cables, and instruction sets used — increases the cost of maintaining systems, research and development, training, and qualifying new products.
Today, parallel technologies still suit users of modern corporate systems in terms of performance, but the growing demand for higher speeds, higher data security during transmission, physical dimensions and broader standardization questions the ability of the parallel interface to keep pace with rapidly growing CPU performance and storage speeds at no extra cost. hard drives... In addition, in conditions of austerity, it is becoming increasingly difficult for enterprises to find funds for the development and maintenance of various types of connectors. rear panels server enclosures and external disk arrays, heterogeneous interface compatibility testing, and heterogeneous connection inventory for I / O.
The use of parallel interfaces also presents a number of other problems. Parallel data transmission over wide stub cables is prone to crosstalk, which can create additional interference and lead to signal errors — avoiding this trap requires slowing down the signal rate or limiting the cable length, or both. Termination of parallel signals is also associated with certain difficulties - you have to terminate each line separately, usually this operation is performed by the last accumulator in order to prevent signal reflection at the end of the cable. Finally, the large cables and connectors used in parallel interfaces make these technologies unsuitable for new compact computing systems.
Introducing SAS and SATA
Serial technologies such as Serial ATA (SATA) and Serial Attached SCSI (SAS) overcome the architectural limitations inherent in traditional parallel interfaces. These new technologies got their name from the method of signal transmission, when all information is transmitted sequentially (English serial), in a single stream, as opposed to multiple streams, which are used in parallel technologies. The main advantage of the serial interface is that when data is transferred in a single stream, it moves much faster than using the parallel interface.Serial technologies combine many bits of data into packets and then transmit them over cable at speeds up to 30 times faster than parallel interfaces.
SATA extends the capabilities of traditional ATA technology by allowing data transfer between disk drives at speeds of 1.5 GB per second and above. Low cost per gigabyte of storage SATA drive will remain the dominant disk interface in desktops, entry-level servers and networked storage systems, where cost is a major consideration.
SAS, the successor to parallel SCSI, builds on the proven functionality of its predecessor and promises to greatly expand the capabilities of today's enterprise storage systems. SAS has many benefits not available traditional solutions in the field of data storage. In particular, SAS allows up to 16,256 devices to be connected to a single port and provides reliable point-to-point serial connections at speeds up to 3 Gb / s.
In addition, with a smaller SAS connector, it provides full dual-port connectivity for both 3.5 "and 2.5" drives (previously only available with 3.5 "Fiber Channel drives). This is a very useful feature when you need to accommodate a large number of redundant drives in a compact system such as a low-profile blade server.
SAS improves the addressing and connectivity of drives with hardware extenders that allow you to connect a large number of drives to one or more host controllers. Each expander supports up to 128 physical devices, which can be other host controllers, other SAS expanders, or disk drives. This design scales well and allows you to create enterprise-scale topologies that easily support multisite clustering for automatic system recovery in the event of a failure and for even load balancing.
One of the major benefits of the new serial technology is that the SAS interface will also be compatible with the lower-cost SATA drives, allowing system designers to use both types of drives in the same system without spending additional funds to support two different interfaces. Thus, SAS, the next generation of SCSI technology, overcomes the existing limitations of parallel technologies in terms of performance, scalability and data availability.
Multiple levels of compatibility
Physical compatibilityThe SAS connector is universal and SATA compatible in form factor. This allows both SAS and SATA drives to be directly connected to the SAS system and thus use the system for either mission-critical applications that require high performance and fast data access, or for more cost-effective applications with a lower cost per gigabyte.
The SATA command set is a subset of the SAS command set, which provides compatibility between SATA devices and SAS controllers. However, SAS drives cannot work with a SATA controller, so they are equipped with special keys on the connectors to eliminate the possibility of incorrect connection.
In addition, the physical characteristics of the SAS and SATA interfaces are similar, allowing the new universal SAS backplane to accommodate both SAS and SATA drives. As a result, there is no need to use two different rear panels for SCSI and ATA drives. This design compatibility benefits both backplane manufacturers and end users by reducing hardware and design costs.
Protocol Compatibility
SAS technology includes three types of protocols, each of which is used to transfer data different types via the serial interface, depending on which device is being accessed. The first is the Serial SCSI Protocol SSP, which sends SCSI commands, and the second is the SCSI Management Protocol (SMP), which transfers control information to the expanders. The third, SATA Tunneled Protocol STP, establishes a connection that allows the transmission of SATA commands. By using these three protocols, the SAS interface is fully compatible with existing SCSI applications, management software, and SATA devices.
This multi-protocol architecture, combined with physical compatibility SAS connectors and SATA, makes SAS technology a universal glue between SAS and SATA devices.
Benefits of compatibility
SAS and SATA interoperability offers a variety of benefits to system designers, assemblers, and end users.
System designers can use the same rear panels, connectors and cable connections due to SAS and SATA compatibility. Upgrading a system from SATA to SAS is essentially a matter of replacing disk drives. In contrast, for traditional parallel users, the move from ATA to SCSI means replacing back panels, connectors, cables and drives. Other cost-effective benefits of sequential technology interoperability include simplified certification and material management.
VAR resellers and system builders can easily and quickly reconfigure custom systems by simply installing the appropriate disk drive into the system. There is no need to work with incompatible technologies and use special connectors and different cable connections. What's more, the added flexibility to balance price and performance will allow VAR resellers and system builders to better differentiate their products.
For end users, SATA and SAS compatibility means a new level of flexibility when it comes to choosing the right price / performance ratio. SATA drives are the best choice for low-cost servers and storage systems, while SAS drives provide maximum performance, reliability and compatibility with control software. The ability to upgrade from SATA drives to SAS drives without the need to purchase a new system greatly simplifies the purchasing decision process, protects your system investment and lowers your total cost of ownership.
Co-development of SAS and SATA protocols
January 20, 2003 SCSI Trade Association (STA) and Working group The Serial ATA (SATA) II Working Group announced a collaboration to ensure system-level compatibility of SAS technology with SATA disk drives.The two organizations are working together, as well as the joint efforts of storage vendors and standards committees, to provide even more precise interoperability guidelines to help system designers, IT professionals, and end users fine-tune their systems to achieve optimal performance. and reliability and lower total cost of ownership.
The SATA 1.0 specification was approved in 2001 and there are SATA products on the market today from various manufacturers. The SAS 1.0 specification was approved in early 2003, and the first products are expected to hit the market in the first half of 2004.
This article will focus on what allows you to connect a hard drive to your computer, namely, the hard drive interface. More precisely, about the interfaces of hard drives, because a great many technologies have been invented for connecting these devices over the entire period of their existence, and the abundance of standards in this area can confuse an inexperienced user. However, about everything in order.
Hard disk interfaces (or, strictly speaking, external storage interfaces, since they can be used not only, but also other types of drives, for example, optical drives) are designed to exchange information between these external memory devices and the motherboard. Hard drive interfaces, as much as the physical parameters of the drives, affect many of the drive's performance and performance. In particular, the interfaces of the drives determine their parameters such as the speed of data exchange between the hard drive and the motherboard, the number of devices that can be connected to a computer, the ability to create disk arrays, the possibility of hot plugging, support for NCQ and AHCI technologies, etc. ... It also depends on the hard disk interface which cable, cord or adapter you need to connect it to the motherboard.
SCSI - Small Computer System Interface
SCSI is one of the oldest interfaces developed for connecting storage devices in personal computers. This standard appeared in the early 1980s. One of its developers was Alan Shugart, also known as the inventor of floppy drives.
External view of the SCSI interface on the board and the cable for connecting to it
The SCSI standard (traditionally this abbreviation is read in Russian transcription as "fairy tale") was originally intended for use in personal computers, as evidenced by the very name of the format - Small Computer System Interface, or a system interface for small computers. However, it so happened that drives of this type were used mainly in top-class personal computers, and later in servers. This was due to the fact that, despite the successful architecture and a wide range of commands, the technical implementation of the interface was rather complicated and did not suit the cost of mass PCs.
Nevertheless, this standard had a number of capabilities that are not available for other types of interfaces. For example, a Small Computer System Interface cable can have a maximum length of 12 m and a data transfer rate of 640 MB / s.
Like the later IDE interface, the SCSI interface is parallel. This means that the interface uses buses that carry information over multiple conductors. This feature was one of the limiting factors for the development of the standard, and therefore, as its replacement, a more advanced, serial SAS standard (from Serial Attached SCSI) was developed.
SAS - Serial Attached SCSI
This is how the SAS interface of a server disk looks like
Serial Attached SCSI was developed as an improvement on the rather old Small Computers System Interface for connecting hard drives. Despite the fact that Serial Attached SCSI takes advantage of the main advantages of its predecessor, it nevertheless has many advantages. Among them, the following are worth noting:
- Use of a common bus for all devices.
- The serial communication protocol used by SAS allows fewer signal lines to be used.
- No bus termination required.
- Almost unlimited number of connected devices.
- Higher bandwidth (up to 12 Gbps). Future implementations of the SAS protocol are expected to support data rates up to 24 Gbps.
- The ability to connect to the SAS controller drives with Serial ATA interface.
Typically, Serial Attached SCSI systems are built around several components. The main components include:
- Target devices. This category includes the actual drives or disk arrays.
- Initiators are microcircuits designed to generate requests to target devices.
- Data delivery system - cables connecting target devices and initiators
Serial Attached SCSI connectors come in different shapes and sizes, depending on the type (external or internal) and the SAS versions. The following is an internal SFF-8482 connector and an external SFF-8644 connector designed for SAS-3:
Left - internal SAS SFF-8482 connector; On the right is an external SAS SFF-8644 connector with a cable.
A few examples of the appearance of SAS cords and adapters: HD-Mini SAS cord and SAS-Serial ATA adapter cord.
Left - HD Mini SAS cord; Right - SAS to Serial ATA adapter cable
Firewire - IEEE 1394
Today you can often find hard drives with Firewire interface. Although you can connect any type of peripheral device to your computer through the Firewire interface, and it cannot be called a specialized interface designed for connecting exclusively hard drives, nevertheless, Firewire has a number of features that make it extremely convenient for this purpose.
FireWire - IEEE 1394 - Laptop View
The Firewire interface was developed in the mid-1990s. The beginning of the development was laid by the well-known company Apple, which needed its own, other than USB, bus for connecting peripheral equipment, primarily multimedia. The specification that describes how the Firewire bus works is called IEEE 1394.
Firewire is one of the most commonly used high-speed serial external bus formats today. The main features of the standard include:
- Hot-pluggable devices.
- Open bus architecture.
- Flexible topology for connecting devices.
- Widely varying data transfer rates - from 100 to 3200 Mbit / s.
- The ability to transfer data between devices without a computer.
- The ability to organize local networks using a bus.
- Bus power transmission.
- A large number of connected devices (up to 63).
To connect hard drives (usually by means of external enclosures for hard drives) via the Firewire bus, as a rule, a special SBP-2 standard is used, which uses the command set of the Small Computers System Interface protocol. It is possible to connect Firewire devices to a regular USB connector, but this requires a special adapter.
IDE - Integrated Drive Electronics
The abbreviation IDE is undoubtedly familiar to most personal computer users. The interface standard for connecting IDE hard drives was developed by the well-known hard drive manufacturer Western Digital. The advantage of IDE over other interfaces that existed at that time, in particular the Small Computers System Interface, as well as the ST-506 standard, was that there was no need to install a hard disk controller on the motherboard. The IDE standard meant installing a drive controller on the drive's case, and the motherboard only had an interface host adapter for connecting IDE drives.
IDE interface on the motherboard
This innovation has improved the performance of the IDE drive due to the fact that the distance between the controller and the drive itself is reduced. In addition, the installation of an IDE controller inside the hard drive case made it possible to somewhat simplify both motherboards and the production of the hard drives themselves, since the technology gave freedom to manufacturers in terms of the optimal organization of the drive logic.
The new technology was originally named Integrated Drive Electronics. Subsequently, a standard describing it was developed, called ATA. This name is derived from the last part of the name of the PC / AT family of computers by adding the word Attachment.
A dedicated IDE cable is used to connect a hard drive or other device such as an Integrated Drive Electronics optical drive to the motherboard. Since ATA refers to parallel interfaces (therefore it is also called Parallel ATA or PATA), that is, interfaces that provide for the simultaneous transfer of data over several lines, its data cable has a large number of conductors (usually 40, and in the latest versions of the protocol it was possible to use 80-wire cable). Regular data cable for of this standard has a flat and wide appearance, but there are also round cables. The power cable for Parallel ATA drives has a 4-pin connector and is connected to the computer's power supply.
Below are examples of IDE cable and round PATA data cable:
External view of the interface cable: on the left - flat, on the right in a round braid - PATA or IDE.
Due to the comparative cheapness of Parallel ATA drives, the ease of implementation of the interface on the motherboard, as well as the ease of installation and configuration of PATA devices for the user, Integrated Drive Electronics drives for a long time ousted devices of other types of interface from the market of hard drives for budget-level personal computers.
However, the PATA standard also has several disadvantages. First of all, this is a limitation on the length that a Parallel ATA data cable can have - no more than 0.5 m. In addition, the parallel organization of the interface imposes a number of restrictions on the maximum data transfer rate. It does not support the PATA standard and many of the advanced features that other types of interfaces have, such as hot-plugging devices.
SATA - Serial ATA
SATA interface on the motherboard
The SATA (Serial ATA) interface, as the name suggests, is an enhancement to ATA. This improvement consists, first of all, in converting the traditional parallel ATA (Parallel ATA) into a serial interface. However, the differences between the Serial ATA standard and the traditional one are not limited to this. In addition to changing the data transfer type from parallel to serial, the data and power connectors have also changed.
Below is the SATA data cable:
Data cable for SATA interface
This made it possible to use a significantly longer cable and to increase the data transfer rate. However, the disadvantage was the fact that PATA devices, which were present on the market in huge quantities before the advent of SATA, became impossible to directly plug into the new connectors. True, most new motherboards still have old connectors and support connecting older devices. However, the reverse operation - connecting a new type of drive to an old motherboard usually causes much more problems. For this operation, the user usually needs a Serial ATA to PATA adapter. The power cable adapter is usually relatively simple in design.
Serial ATA to PATA Power Adapter:
Left general form cable; On the right, the external view of the PATA and Serial ATA connectors is enlarged
More complex, however, is the case with a device such as an adapter for connecting a serial device to a parallel interface connector. Usually, an adapter of this type is made in the form of a small microcircuit.
Appearance of the universal bi-directional adapter between SATA interfaces- IDE
Nowadays the Serial ATA interface has practically supplanted Parallel ATA, and PATA drives can now be found mainly only in fairly old computers. Another feature of the new standard that has ensured its widespread popularity is support.
Type of adapter from IDE to SATA
You can tell a little more about NCQ technology. The main advantage of NCQ is that it allows you to use ideas that have long been implemented in the SCSI protocol. In particular, NCQ supports a system for sequencing read / write operations coming to multiple drives installed in the system. Thus, NCQ can significantly improve the performance of storage devices, especially hard disk arrays.
SATA to IDE adapter
To use NCQ, technology support is required from the hard disk side as well as the motherboard host adapter. Almost all adapters that support AHCI also support NCQ. In addition, NCQ is supported by some older proprietary adapters. Also, for the operation of NCQ, its support from the operating system is required.
eSATA - External SATA
Separately, it is worth mentioning the eSATA (External SATA) format, which seemed promising in its time, but has not received wide distribution. As you might guess from the name, eSATA is a type of Serial ATA designed for connecting exclusively external drives. The eSATA standard offers for external devices most of the capabilities of the standard, i.e. internal Serial ATA, in particular the same system signals and commands and equally high speed.
ESATA connector on laptop
However, eSATA has some differences from the internal bus standard that gave rise to it. In particular, eSATA supports longer data cables (up to 2m) and also has higher power requirements for drives. In addition, eSATA connectors are slightly different from standard Serial ATA connectors.
Compared to other external buses such as USB and Firewire, eSATA, however, has one major drawback. While these buses allow the device to be powered through the bus cable itself, the eSATA drive requires dedicated power connectors. Therefore, despite the relatively high data transfer rate, eSATA is currently not very popular as an interface for connecting external drives.
Conclusion
The information stored on the hard disk cannot become useful to the user and accessible to application programs until it gets access CPU computer. Hard drive interfaces are the means for communication between these drives and the motherboard. Today there are many different types hard disk interfaces, each of which has its own advantages, disadvantages and characteristic features. We hope that the information given in this article will be in many ways useful to the reader, because the choice of a modern hard disk is largely determined not only by its internal characteristics, such as capacity, cache memory, access and rotation speed, but also by the interface for which it was designed.