How to choose a storage system? Data Storage Systems DAS, NAS, SAN. Distributed Antenna Systems (DAS)

If multi-disk network storage devices (NAS, Network Attached Storage) have long and firmly entered the everyday life of users of personal computers, home entertainment centers and offices of small companies, then their counterparts without a network interface, using a direct connection to a computer (Direct Attached Storage, or just DAS), although they have been on the market for a very long time, they have not yet received such wide distribution. The reasons for this lie, on the one hand, in the fact that the network interface and the ability to share NAS are more versatile (and the NAS themselves are much more multifunctional than DAS), and on the other hand, one- and two-disk external drives with USB, FireWire and / or eSATA is even more widespread than NAS, so the need for DAS for 4-8 disks may arise for a very limited number of consumers who have actually decided to significantly expand the disk space of their computer (desktop, laptop or non-critical server) or media center by external , and not the internal connection of several hard drives, combined, as a rule, into an array.

The advantages of using DAS in comparison with NAS are in the extreme ease of installation and use (DAS can be simply connected to any PC, media player, etc. with a USB or eSATA cable and it will immediately start working in the system as an external disk; the disk array is configured with a simple jumper), and also in a higher speed (after all, USB 3.0 and eSATA are noticeably faster than Gigabit Ethernet). And compared to conventional external USB / eSATA hard drives, DAS allows you to conveniently use more disk space by simply organizing a RAID array of several disks (including information protection) and increase the speed of operation in relation to single external hard drives (i.e. actually squeeze the maximum possible speed out of the eSATA and USB 3.0 interfaces).

In addition, with the help of DAS, you can also expand the storage capacity of the NAS, if the latter has an eSATA or USB port.

Well, compared to increasing the disk capacity of a PC by installing internal hard drives - DAS allows you to avoid "picking" inside the system unit (by the way, not always the power supply unit and the motherboard have 4-5 free SATA connectors) and also offers a complete and a convenient external construct (a basket with a power supply unit and electronics), which, by the way, is more convenient to carry than an entire system unit or several external hard drives. With the current capacity of hard drives up to 4 TB, for example, the 5-disk DAS discussed in this review will provide you with a good fast and portable 20 terabyte storage.

Device and characteristics

CFI-B8253JDGG is actually a 5-disk SATA basket in a stylish case with an integrated power supply and uncomplicated electronics for port animation, hardware support for RAID of different levels (with caching) and servicing eSATA and USB 3.0 ports.

DAS CFI-B8253JDGG for 5 hard drives

The device manufacturer, the Taiwanese company CFI Group (Chyangfun Industry Company,), traces its history back to 1987 and positions itself as a leading manufacturer of PC cases and racks, as well as customized chassis, barebones and media center cases, disk cages, etc. The company manufactures them both in Taiwan and at its factory in China (CFI China, Fongfun Industry Company), founded in 1997.

Among the latest products of the company, I especially liked the unusual Full-Tower case CFI-A1028, shown at the last Computex exhibition,

which allows you to install two motherboards at the same time - a powerful gaming ATX and a compact Mini-ITX (each with its own power supply).

However, I was distracted. :)

DAS CFI-B8253JDGG comes in a black and green box with illustrations and basic product description.

The set includes three cables (network, USB 3.0 and eSATA - 120 cm long), an eSATA bracket for a PC, screws for attaching 3.5-inch drives in sleds and a CD with documentation (the latest version of the documentation and the RAID configuration and management software -array CFI can be downloaded at). The site also provides information about CFI DAS in Russian and indicates the address of the corporate service center in Russia.

The manufacturer describes the main properties of this product as follows:

• Fault-tolerant storage system based on a hardware RAID controller.
• High-speed data exchange during storage, working with archives and local backup.
• An effective tool for increasing the level of reliability of the storage system and reducing the costs associated with downtime or information recovery.
• Maximum performance when working with data.
• Low cost compared to other storage technologies (NAS, SAN).
• Comfortable operation: the fastest possible introduction into operation, simple configuration of RAID-array modes, which does not require special technical knowledge; to work with a RAID-array, you do not need to install additional software or any settings in the BIOS of the PC / server to which the DAS is connected CFI drive.

Basic specifications DAS CFI-B8253JDGG

Body material and color	steel, ABS plastic; black
Number of bays for HDD 3.5 / 2.5 ″	5
Disk interface	Serial ATA 3Gb / s
External interfaces	USB 3.0 and eSATA 3Gb / s
RAID levels	0, 1, 3, 5, 10, JBOD, Clone (N-way Mirror)
Nutrition	built-in power supply unit 110-240 V, 250 W
Fans	120 mm (HDD cage) and 40 mm (in PSU)
LED indicators of operation	Power, PC Link, 5 HDD
Dimensions, weight without discs	150 x 214 x 282.5 mm (W x H x D), 4.2 kg
Manufacturer's warranty	1 year
Current average retail price in Moscow	$ 274 (on 01/11/16)

External DAS drives CFI are built on the basis of a hardware RAID controller, which allows them to be directly connected via eSATA or USB (2.0 / 3.0) to PCs, laptops, NAS, servers, media players and other host devices without installing additional software. DAS will work even with a tablet / smartphone with a USB host function. And if you connect it via USB to a router, it will become available to any user over the local network. In addition, installing CFI proprietary software on a PC will provide an expanded set of functions: configuring and monitoring the status of the RAID array, e-mail notification, firmware updates, etc. (see below).

The drive is housed in a glossy black steel case with an ABS front panel with rounded upper and lower ribs. The relatively small "footprint" of the case, supported by decent rubber feet, allows it to be installed almost anywhere near the necessary electronics - PC, laptop, media player, etc. And the stylish appearance and unobtrusive indicator light will not disturb the interior of a home entertainment center or “ modern "office.

The discs are installed in the DAS cage from the front - in a sliding sled, covered with a decorative door with a metal ventilation grill.

The sleds are made of 0.8 mm steel, have a convenient locking mechanism in the basket (with ventilation holes at the front ends), practically do not play and allow you to mount both 3.5-inch and 2.5-inch drives (screws for the latter are included in the delivery set, however, not). The disks have close direct contact with the metal of the sled (no shock absorbers are provided), and the sled with the metal of the DAS chassis, therefore heat removal from the disks is carried out both by direct heat transfer from the hard disks to the case parts, and by a through ventilation system (a quiet 120 - millimeter fan), due to which high efficiency of system cooling is achieved. The gap between the discs in the basket is about 4 mm.

We tested the cooling properties of the DAS design by installing five 3.5-inch Seagate Barracuda XT 3TB drives and their maximum access load (random reads of each drive in 4 KB blocks) while measuring the temperature of each of them. The temperature of all disks after an hour of testing was in the range of 38-40 ° C, which can be considered a very good result (in real work, DAS disks will be even cooler).

At the same time, the 120-mm system fan works relatively quietly (although it could have been made even quieter, and without much damage to the cooling of the disks!) solutions using "thin" power supply units. In general, his night work is still unsuitable for a bedroom, and even being on a desktop next to an office or home PC, he will "ride" a little on his ears. In any case, the 5-disk NAS standing next to my PC is much quieter and "invisible" by ear than CFI-B8253JD.

By the way, the sled has light guides that transmit green light from the indicators on the internal panel of the SATA connectors to the front DAS panel, so you can see through the grille of the front door which drives are on and working. However, the main indicators of DAS operation are located outside - at the bottom of the front panel, to the left of the power switch.

Square orange indicates power is on, green PC Link indicates eSATA or USB connection to a PC (or other host), and five indicators on the left indicate the status of the respective HDDs (drives in the basket are numbered from top to bottom): green indicates normal operation (blinking green, if the corresponding HDD is being accessed), blinking red means the array is being rebuilt, and solid red means a disk failure. The indicators do not blind the eye in the dark, but they are clearly visible in the light.

DAS power is turned on not with a “non-fixed” button, as in the overwhelming majority of ATX PC cases, but with a latched edge switch (as it was, for example, in AT cases). This allows, in particular, to completely de-energize the DAS PSU in the off state and thereby save energy.

On the rear panel of the DAS chassis there are power connectors, eSATA, USB 3.0, exhaust outlets for two fans, and a microswitch for selecting the type of RAID array (see below for details). By the way, there is a “Made in Taiwan” sticker on the DAS case. :)

Inside the DAS case, under the outer shell of 0.7 mm steel, there is enough room: there is a lot of free space both above and below the disk cage, and on the sides, and between the disks and the propeller. Apparently, the body of this DAS, with a special desire, could have been made more compact by one and a half times in volume. However, this cannot be recognized as a disadvantage - reliable cooling and low price are more important.

Front view of the main DAS board

System propeller model A12025M12S manufactured by You Fu Li Electronics Co. for a maximum current of 0.32 A, it is protected by an internal mesh from accidental penetration of cables. It is three-wire, with a speed sensor, but in this DAS is connected via two wires.

The CFI-250AT-1U universal power supply unit (from the name of the model it is clear what format and standard) with an output power of 250 W is designed for output currents of 18 A and 10 A along the voltage lines +12 V and +5 V, respectively, has dimensions of 81 × 150 × 44mm and has its own 40mm fan and a pair of 4-pin Molex connectors for connecting to the DAS backplane.

The power of this PSU may seem clearly excessive for a 5-disk SATA cage that does not support SAS drives, since a typical capacious modern SATA hard drive consumes 3-7 W in idle and 7-12 W in active operation, that is, in fact, no more than 60 Watts in operation for the whole basket. However, if we take into account that some disks (for example, Seagate) at the time of start (and in this DAS, all disks start simultaneously) can consume current up to 2.5-2.9 A from a voltage of +12 V (that is, almost 18 A per basket), the developers' repeated reinsurance at the power supply rating does not seem excessive anymore - after all, 18 A on the 12 V line is the passport (and peak) limit for this power supply model.

The electronics of this DAS is based on two printed circuit boards - main and additional. The main board contains connectors for connecting hard drives (with power supply), a fan, indicators, an eSATA port, etc.

Main electronics board DAS CFI-B8253JDGG on both sides

There is also the RAID controller itself - a chip for 6 SATA 3 Gb / s ports, supplemented by a SATA 3 Gb / s duplicator port on the chip. Both chips, by the way, were developed back in 2008, when SATA 6 Gb / s existed only in the minds of the creators of standards.

JMicron JMB394 controller (left) with JMB320 port duplicator (right)

Manufactured using 130nm manufacturing process, it has a built-in high-performance RAID processor with cache memory for on-the-fly servicing of parity (RAID 3 and 5) and mirrored (RAID 1, 10, Clone) arrays, freeing the processors host computers.

JMicron JMB394 controller block diagram

The speed of automatic rebuilding of arrays on this processor reaches 200 GB / h (below we will test it too), the chip supports disks with a volume of more than 2 TB and sequential promotion of drives (the work of the latter in this DAS, it seems, is not implemented - but in vain; see above about the power supply unit and its "ringing" propeller). The JMB320 duplicator port doubles the SATA host interface of the JMB394 chip to connect an eSATA port and a USB 3.0 interface translator. When two hosts are simultaneously connected to DAS (via eSATA and USB), the one that uses eSATA works, which is convenient to use when simultaneously connecting DAS, for example, to a desktop (via eSATA) and a media player or router (via USB).

On the second, additional board, there is only a USB 3.0 to SATA interface converter on the chip and the corresponding connectors. The USB 3.0 board sits on the bottom of the case next to the PSU, bringing the USB connector to the rear panel, and connects to the main board via SATA and power cables.

It is curious that the controller manufactured according to the 130-nm technological process (by the standards of the IT industry, it is quite "ancient" - the development of the end of 2009) is based on the well-known 8051 architecture (in particular, in the early 90s it was very popular in Russian " Caller ID ":)), albeit with 25 MHz clocking, 60 MIPS performance and built-in USB encryption over AES-128/256.

Of course, DAS can also be connected to the old host ports of the USB 2.0 interface (with a corresponding decrease in operating speed relative to SuperSpeed ​​USB).

Two more mini-cards in CFI-B8253JD carry front panel indicators and RAID mode switches (the latter is attached to the rear panel of the case).

In general, it seems that the design solution for this DAS is aimed not so much at elegance (in terms of approaches) and compactness, but at low cost of production and versatility (multivariate use of individual components). Obviously, this is due to the still not very large volume of sales of these devices.

DAS supports Serial ATA 3Gb / s hard drives and most SATA I (1.5Gb / s) hard drives. Modern SATA 6 Gb / s drives also work seamlessly in it - at 3 Gb / s speeds. The eSATA port in this DAS also operates at a maximum of 3Gb / s, although it is compatible with modern 6Gb / s SATA controllers. SAS disks cannot be installed here, even mechanically. Drives can be installed in the basket in any order (in any combination of bays), but it is most convenient to immediately fill all 5 bays with discs of the same capacity.

Configuration and operation

No special drivers are required for DAS to work with a computer, media player, etc. The device is defined as a standard external drive and immediately starts working with the host in this mode.

The controller used in DAS has a hardware implementation of RAID levels 0, 1, 3, 5 and 10, and can also work with drives in Clean, Large and Clone modes. For RAID arrays, write caching, automatic rebuilding of arrays (except for RAID 0), the ability to rebuild the array in the background at a speed of up to 200 GB per hour, and the ability to hot swap drives (in Clone, R1, R3, R5, R10 configurations) are supported.

Storage mode Large is actually equivalent to JBOD - it simply combines a group of physical hard disks installed in a DAS into a single array. In this case, the size of the array available for data storage is equal to the sum of the capacities of each disk, and the speed at each point in space corresponds to the speed of a single disk used at the moment (see, for example, the following graph of the linear read speed of such an array of five disks of the same size) ...

Linear read speed (according to AIDA64) of a Large (JBOD) array of 5 identical disks in DAS CFI-B8253JD

Large mode provides maximum storage space while using discs miscellaneous volume. Recall that in RAID levels 0, 1, 3, 5 and 10, arrays will be organized based on the size of the smallest disk installed in the system. In this case, the "extra" (remaining after the organization of the array) space on larger drives in this DAS will not be able to be used.

In storage mode Clone the information stored on DAS CFI is duplicated on all hard drives installed in the device. When using this mode, the size of the array available for data storage is equal to the smaller HDD installed in the drive. This achieves the maximum level of reliability of the data storage system. In the event of a simultaneous failure of several disks, the files recorded on the DAS CFI can be restored using the remaining functional disks. Clone mode can also be used for information replication tasks.

In storage mode Clean each disk installed in DAS CFI is defined as a separate local hard disk of the host device (PC, server, media player, laptop, NAS, etc.). In this case, you can install / change disks with already recorded information in DAS, use HDD of different capacities and not worry about the safety of data recorded on the disk. When installing HDD in DAS CFI in this storage mode, you do not need to format hard drives if they already have data, as well as when using external USB or eSATA drives.

However, it should be remembered that in order to access all DAS CFI hard disks via eSATA interface in Clean mode, the SATA controller of the motherboard (host device) must support a full port multiplier mode (PM, Port Multiplier): the host device motherboard must have a full eSATA port, and not its emulation, in the form of an eSATA connector connected to a regular SATA port, and PM support must be explicitly indicated in the motherboard passport. If this mode is not supported, then when DAS CFI is connected via eSATA, the operating system of the host device recognizes only the first DAS CFI disk. Unfortunately, the built-in SATA controllers of almost all modern (and earlier) "desktop" and mobile chipsets for PCs lack support for port multiplication, so this function can only be used here by connecting DAS to the SATA port of some discrete controllers (for example, companies Marvell). Fortunately, when DAS is connected via USB, this problem is not - in Clean mode, all disks are visible separately:

Disks installed in DAS CFI are visible individually only in Clean mode, provided they are connected via USB or if the eSATA host supports port animation

At the same time, we repeat that if the CFI-B8253JD is connected to a PC via eSATA and USB at the same time, then the eSATA connection will be active. This can be used, for example, to connect two devices to DAS at once: a PC via eSATA and a media player (or router / tablet / laptop) via USB. When the PC is turned off, the DAS is automatically accessed by the media player / router.

Before connecting a DAS with newly installed drives for the first time to a host device (PC, server, NAS, etc.), you must select the storage array mode you plan to use. To do this, without turning on the DAS power supply (!), You need to set the required combination of the positions of the microswitches on the rear panel of the DAS according to the label given there.

After that, press (for example, with a pen or tweezers) on the secret Reset button on the back panel next to the microswitches and, while holding it down, turn on the DAS power with the toggle switch on the front panel (obviously, you cannot do all this with one hand). The Reset button must be held down for five seconds from the moment the power is turned on. During this time, the DAS controller recognizes the connected disks and organizes them into the desired array. After this procedure, the DAS will operate in the selected mode regardless of power outages.

After replacing the disk (s) in the DAS or if you want to change the type of the array, you must repeat the above procedure again. It should be remembered that all information on hard disks installed in the DAS drive will be deleted during the initial initialization of the storage array. Hot swap drives are only available for RAID 1, 10, 3, 5, and Clone.

Configuring DAS for Windows

However, it is much more convenient to manage DAS CFI-B8253JD arrays in Windows / MacOS using the proprietary Hardware RAID Manager utility.

In it, you can not only view detailed information about the disks installed in the DAS,

and also view the current SMART information for each of the disks separately

and a log file of DAS work lately,

but also customize many parameters. In particular, the ability to configure disks into a RAID array in this utility is very useful. Moreover, this can be done in the Basic mode (simplified version of the settings),

and in Advanced mode (more detailed settings option).

Here you can set one of the above array types, and in Advanced mode you can even mark which disks installed in the DAS basket should be used to organize this array.

In addition, you can set a password to access the array,

and also remove the array:

In the Advanced mode of the Hardware RAID Manager utility, another function for configuring arrays is available, which is not possible with the hardware (jumpers) method of specifying the array type. The fact is that the utility can be used to configure more than one array common to all DAS disks, but to combine the basket disks into several simultaneously operating arrays. For example, in the following screenshot, the 5 drives in the cage are organized into two arrays - one RAID 1 of a pair of drives and the second RAID 5 of three drives.

However, it should be borne in mind that this will only work if the DAS is connected to the host via USB or eSATA with the support of the port animation mode on the host side. Thus, the flexibility of using the disk cage in DAS when configuring arrays programmatically increases significantly.

A useful addition is the ability, using the configuration utility, to set the method for notifying the administrator by e-mail about certain events occurring with the DAS,

as well as the ability to update the device firmware:

In addition, on a separate settings screen, you can set the priority for RAID rebuilding and the time (in minutes) when it goes to sleep:

This utility makes working with DAS much more fun. However, you can use the CFI-B8253JD without this, simply by configuring the array in hardware using microswitches on the rear panel of the case and connecting it via one interface or another to almost any host device.

Performance testing

To test the speed of the CFI-B8253JD, we used the test system in the following configuration:

• Intel Core i7-2600 processor;
• 2 GB DDR3-1333 memory (two modules);
• motherboard Gigabyte GA-Z68XP-UD3-iSSD;
• video card based on AMD Radeon HD 5450;
• System SSD 120 GB (SATA 6 Gb / s);
• OS MS Windows 7 Ultimate x64 SP1.

This motherboard is convenient because it allows you to use not only one of the fastest USB 3.0 controllers on the EtronTech EJ168A chip, but also the latest generation SATA controllers of the desktop class: Intel 6/3 Gbps in the Z68 Express chipset and a separate Marvell ( chip 88SE9172) at 6 Gb / s on the PCIe bus. The latter, in particular, supports SATA port multiplication, which is necessary for the full use of several independent drives in this DAS with an eSATA connection.

For performance tests in DAS CFI-B8253JD, five high-performance and economical Seagate ST91000640NS hard drives with a rotational speed of 7200 rpm platters were installed. , at the level of 12 ms, which, for example, numerous "barracudas" and "caviar" cannot boast of. Their linear access speed is at the level of "green" drives, but this is not critical in this case, since the hard drives are combined into arrays with the final linear access speed, as a rule, noticeably higher than the throughput of USB 3.0 and eSATA 3 Gb / s interfaces.

When testing the speed of DAS, just in case, we compared the performance when connecting DAS to SATA ports of both 3 Gb / s and 6 Gb / s of the Z68 chipset (for the variant with RAID 0) - the tests naturally showed the similarity of the results within the margin of error , so all other measurements were taken when connected to the SATA 3 Gb / s port of the Z68 chipset in AHCI mode.

When connecting DAS via USB 3.0, we used not only the Etron EJ168A board controller and the Intel chipset USB 2.0 controller, but also a separate discrete USB 3.0 controller card on the ASMedia ASM1042 chip. However, in the latter case, the operating speed turned out to be noticeably lower than for the EJ168A, so we will not demonstrate these results here. In addition, as it turned out, when connected via USB 3.0, the CFI-B8253JD works quite capriciously. This is reflected both in a sharp decrease in speed (several times relative to the maximum achievable level in practice - almost to the speed when the use of USB 3.0 in comparison with USB 2.0 already makes no sense), and in the fact that DAS often "falls off" from the system just in the course of inactivity of the PC or when transferring data via USB, thereby delivering a lot of trouble to the user. This happened with both USB 3.0 controllers we used. And since when "flipping" DAS to eSATA or USB 2.0 (without any other changes in the configuration of the test system) in this case, no problems with stability and speed were observed, and besides, these USB 3.0 controllers simultaneously demonstrated almost flawless operation with other USB 3.0 drives, we are forced to conclude that there are problems with the stability and speed of the USB 3.0 interface in DAS CFI-B8253JD.

Through long experiments, we managed to achieve more or less stable and fast operation of CFI-B8253JD via USB 3.0 only when the DAS power cable was located in the mains filter socket adjacent to the PC power supply cable, and in the same "polarity" connection. In the rest of the cases, it was impossible to obtain results of any significance for use in this review. Once again, we did not observe any whims in the CFI-B8253JD for eSATA connection. True, when connected to eSATA, CFI-B8253JD does not use NCQ:

In addition, for comparison, we also used a typical NAS based on the Intel Atom platform - Synology DS710 +. It will represent the performance of a typical NAS with a gigabit network interface at a price comparable to the CFI-B8253JD. The NAS was supplied with the same hard drives and connected to the same test system as the DAS.

To test the performance and stability of the DAS, we used the following applications:

• ATTO Disk Benchmark 2.46
• AIDA64 2.20 Disk Benchmark
• Futuremark PCMark 7
• Intel IOMeter 2006
• Intel NASPT 1.7.1
• HD Tach RW 3.0

The test results are summarized in a separate table available for download, and only the most important indicators are shown on the diagrams.

The most indicative are the results of tests of the maximum speed of reading and writing large files in ATTO Disk Benchmark. These figures give us the actual maximum values ​​of the DAS speed during sequential read and write operations (by the way, in the AIDA64 and HD Tach RW tests, similar indicators for both linear and buffered operations turned out to be noticeably lower than in the ATTO benchmark).

The speed of the arrays on the CFI-B8253JD is ranked in accordance with the theory: the fastest is 5-disk RAID 0 (it is actually limited only by the speed of the SATA 3 Gb / s interface - about 260 MB / s for reading and 230 MB / s for writing). This is followed by 5-disk RAID 3 and 5, and when reading on eSATA, they are practically not inferior to RAID 0, and when writing, the difference of 1-2% can be neglected. This indicates the high performance of the XOR processor built into the RAID controller of this DAS. This is followed by 4-drive RAID 10 on eSATA, which is only slightly inferior in performance to the RAID 0/3/5 arrays on the drives used here.

The third group of results is formed by all arrays (RAID 0/3/5/10) when connected via USB 3.0. Here, from this DAS, we managed to squeeze out the speed in the region of 200 MB / s when reading and writing (recall the high instability of CFI-B8253JD on this interface), which can be considered quite worthy in comparison, for example, with a gigabit network interface (the last line of the diagram - NAS DS710 +). And in comparison with eSATA, the loss of USB 3.0 is not so fatal as, for example, of USB 2.0 and Gigabit Ethernet (the last three lines of the diagram are above).

A single disk, as well as its equivalent in terms of performance, arrays Clone and JBOD (Large; see the graph in the paragraph "Configuring and Operation") demonstrate here the speed at the level of NAS DS710 + (110-130 MB / s), which is due, in particular, to the performance of the hard drives used for these tests. In general, this inexpensive DAS is able to provide about twice the speed of working with large files than a modern NAS of the same capacity with one gigabit network interface.

A more nontrivial picture is observed in the parameter of the average access time to the DAS array when reading and writing:

When reading the corresponding characteristics of a single disk, the results of arrays of levels 0, 10, JBOD and Clone correlate well, and practically regardless of the DAS connection interface. Arrays of levels 3 and 5 show a noticeable increase in the average random access time when reading, which is obviously caused by the DAS controller delays in XOR operations. Note that for RAID 3, they turn out to be smaller than for RAID 5, although these two arrays have very similar mechanisms of operation (the first uses a dedicated disk for XOR data, while in RAID 5 XOR information is distributed equally between all the disks in the array) ...

The speed advantage of RAID 3 over RAID 5 for the CFI-B8253JD is most clearly seen when small blocks are randomly written (Write Access Time in the diagram above). Yes, both of these arrays are significantly inferior to the others in terms of random write speed, but RAID 3 is still one and a half times faster than the "five" here. Fortunately, in real applications typical for DAS of this class, the share of random writes within the entire volume is small, so the practical difference in speed between RAID 3 and 5 is hardly noticeable here (see below). Note also that the JMicron JMB394 caching controller gives RAID 0 and JBOD arrays a huge (almost five times!) Odds in random write speed compared to other configurations (RAID 10, Clone, Single).

We emphasize that we did not find any significant difference in random access time when DAS was connected via eSATA or USB 3.0. Only for USB 2.0, the random read time increases by 0.1-0.2 ms.

More complex than just copying a large file from / to DAS (which we have already evaluated using the ATTO test), we test the scenarios for using an external drive using the Intel NASPT 1.7.1 and Futuremark PCMark 7 benchmarks. Detailed results for each of the test scenarios can be found here. can be found in the table, and on the diagrams we will give only the final indicators averaged over different test scenarios.

As you can see, the eSATA interface is beyond competition: the same DAS over USB 3.0 works 20% slower, and with USB 2.0 the difference is generally 4 times. At the same time, the presence of fast USB 3.0 can greatly increase the attractiveness of DAS if the computer does not have an eSATA port, but there is USB 3.0. Compared to a gigabit network link, a NAS has an advantage in the speed of practical operation of such a DAS from one and a half to two times.

The RAID 0 array is naturally the leader in performance, but the rest of the multi-disk configurations, including those with parity control, lag behind the leader a little, which makes it possible to use protected arrays of the maximum possible capacity in CFI-B8253JD (RAID 5 and 3 ). The use of the JBOD (Large) array in this DAS is hardly advisable at all - except for combining disks of different capacities.

As for the Secondary Storage tests of the PCMark 7 package, here, unfortunately, the Futuremark benchmark turned out to be powerless to explain to the user the difference in speed between arrays and interfaces. And the reason for this is the specific tracks of this package, during the execution of which Windows caching is actively used on relatively small "initial" sections of external drives.

Array recovery speed

The CFI-B8253JD controller supports automatic rebuild / rebuild of an array in the event of a failure, for example, one drive in an array with parity. It is enough to remove one of the cage disks from a working DAS and then insert it (or its equivalent) again (hot), and the DAS firmware will issue a corresponding error notification, “pick up” the “new” disk and start rebuilding / rebuilding the array. In this case, the array remains available for the user to work with data, although the speed of access to it decreases somewhat.

In the DAS settings from the Windows manager (see above), you can set the priority for the DAS controller to rebuild an array in relation to user actions with files on this array.

We tested how a particular level of array rebuilding priority affects the speed of reading and writing large files to DAS. Tests were carried out in ATTO Disk Benchmark with DAS connected via USB 3.0.

Compared to the speed of a healthy array (top line of the diagram), when rebuilding with the default priority, the speed drops by about half. If you want the minimum loss of speed of working with the array, you can set the lowest rebuild priority.

Then the speed of reading-writing files on DAS will drop by only 10-15%. If you want the fastest recovery of the array, then in the highest priority mode, the file reading speed will drop to 67 MB / s, and the write speed will drop to an insignificant 20 MB / s. Apparently, the "default" setting is the most optimal, allowing you to combine an acceptable recovery speed of an array with a decent speed of reading / writing files on it.

The time to rebuild a RAID 3 array from five 1-terabyte drives (volume size - 4 TB) without external influences (reading / writing files) was about 230 minutes, which in terms of the speed of rebuilding the array gives about 290 MB / s in terms of the size of the array (the amount of data read) or an average of 72.5 MB / s in terms of the speed of writing XOR data to disk. In other words, this is a fairly productive solution.

Conclusion

The 5-disk DAS CFI-B8253JD performed well on the whole. Stylish glossy black case with convenient mounting of drives and good cooling, "correct" indication of modes and a useful utility for managing arrays for Windows allows you to create a fairly compact disk storage with a capacity of up to 20 TB, which is convenient to use by direct connection via eSATA and USB not only to a PC , laptops or low-cost servers, but also media players, tablets, routers and NAS. Ease of configuration and fairly reliable and fast operation, including in RAID 3 and 5 arrays, makes it a real rival of NAS similar in capacity with a gigabit network interface for a number of consumers who do not need flexible network functionality of disk storage, but more importantly, ease of installation, high speed of operation and low cost of the solution (after all, DAS should be cheaper than NAS similar in capacity).

The eSATA interface provides the speed of linear access to the fastest arrays at the level of about 230-260 MB / s, for USB 3.0 the speed turned out to be limited at 200 MB / s, that is, it significantly cuts the theoretical performance of 5-disk RAID 0, 3 and 5 arrays In these circumstances, it is unfortunate that the DAS does not support the 6Gb / s eSATA interface. On the other hand, arrays with parity (RAID 5 and 3), which usually (on simple "chipset" controllers) have a noticeable drop in performance compared to RAID 0 and 10, almost do not lose speed here. This is due to the good hardware implementation of XOR calculations in the JMicron controller.

Despite the fact that the CFI-B8253JD uses a very ancient (by IT standards) element base of the 2008-2009 model, it still has "childhood diseases" and points that I would like to improve / fix. This is the instability of work over USB 3.0, which sometimes makes it almost impossible to use this DAS over USB 3.0, and not quite low-noise operation, and an excess of internal space (if desired, the case could be made one and a half times more compact). However, the CFI-B8253JD copes well with its main functions, and therefore on the way to the consumer, the last question arises: what about the price?

And here the dog rummaged. The fact is that the current retail price of CFI-B8253JD in Russia at the level of 8000 rubles, especially in the period of considerable prices for the hard drives themselves, seems to us somewhat overestimated. After all, for close money, you can buy, for example, the same HP MicroServer (of similar capacity, but much more multifunctional) or 4-disk NAS from some manufacturers. By the way, around 6000 rubles. you can also find a 4-disk DAS. In addition, for the same 8 thousand rubles. You can now buy a couple of "extra" external hard drives of decent capacity, and the disks reserved for DAS can be placed in a PC case "almost free". In general, we think that such a price for DAS CFI-B8253JD, partly due to insufficient sales in the world, may become a noticeable obstacle on its way to a wide Russian consumer, even despite the attractiveness of this solution as a whole.

We are grateful to InPrice for the NAS provided for the test, East-Side Consulting for the Seagate hard drives provided for testing, as well as the F-Center computer store.

09/12/2005, PN, 09:09, Moscow time

In some countries of the world, the government has long obliged companies to store information about all transactions and all correspondence with partners for a long time, which forces enterprises to spend huge sums on corporate data storage systems. Russia does not yet have such a law, but in order to meet the requirements of foreign investors, Russian companies are also forced to spend significant amounts on corporate storage facilities. The selection is most often centered around the top three technologies.

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SAN vs. NAS and DAS

The most promising technologies for building corporate data storage today are recognized as SAN (Storage Area Network) storage devices, devices for direct connection to DAS (Direct Attached Storage) servers, and NAS (Network Attached Storage) devices connected via the Internet.

Comparative characteristics of storage systems

Characteristic	NAS	SAS (DAS)	SAN
Data transfer protocols	CIFS, HTTP, NFS, FTP	SCSI, SSA	SCSI
Transmission speed	at least 100 MB / s per port	several hundred MB / s	up to 1 Gb / s per port
Network protocols	TCP / IP over Ethernet, FDDI, ATM, Gigabit Ethernet	SCSI server interface, network protocol unacceptable	Fiber Channel, Gigabit Ethernet
Scaling	High quality, but reduces network bandwidth	Limited by the number of connected devices and the performance of a single server	The most effective
Data migration	Backup / restore methods used	Reduces server performance	Provides the construction of storage systems of high availability with the possibility of duplication in real time

Source: CNews Analytics

DAS - directly to the server

DAS is connected directly to the server, which is why it is also called SAS (Server Attached Software). Other servers can only be accessed through the owner's server. An external RAID array connects to one or more servers via SCSI or FC (Fiber Channel), with each of these ports available to only one server. The main advantage of SAS over other options is low cost and high performance (when calculating - one storage system for one server). At a relatively low cost of equipment, SAS systems are good for storing streaming media data due to the high speed of exchange with disks, as well as the ability to build capacious systems. SAS is the ideal solution for small and medium-sized companies as well as individual users.

But traditional data storage, which involves a direct connection to the server, has a number of significant drawbacks. Since SAS uses a local network to transfer data, when several servers with storage systems are connected, the load on the local network increases greatly. Therefore, users will not be able to receive information for a long time. SAS solutions also prevent multiple servers from sharing data files. In addition, they are limited by the small distance between the server and the data warehouse systems. And yet, today many Russian customers prefer SAS solutions. Since one of the main advantages of this solution is its low cost.

The volume of information is growing every second at a tremendous speed. Every day a couple of new films are released in the world, an interesting computer game appears every week, and new episodes of your favorite TV series are uploaded to the network with an enviable frequency. In order for you to always be able to save all these files, CFI external DAS-drives were created with support for disks of any size and a USB 3.0 interface.

Was ist DAS?

Benefits and benefits of CFI DAS drives

You will learn the answer to this question from our today's review. Using the example of affordable and sufficiently capacious storage, we will tell you about DAS devices and their areas of application, as well as what the main difference between a DAS drive and a NAS server is, and why you should not overpay for a NAS.

CFI B8253JDGG or NAS Server?

Both DAS and NAS are storage devices. However, a NAS server has one important property: unlike a DAS, a NAS server is an independent device, and has everything you need for autonomous operation: a network interface, software, control hardware, and in some cases even a display. The NAS server can be used without a computer - for example, remotely save photos from a smartphone from a vacation, or watch movies from your home collection at the workplace from a tablet, connecting to the NAS server as a "cloud".

In turn, a DAS drive (an abbreviation for Direct-attached storage) is not capable of any deliberate independent actions, however, in most cases it is more convenient and profitable. DAS is an external box with a hardware RAID controller with convenient access to hard drives, which must be connected to the USB or eSATA port of a computer, laptop or router with USB storage support.

Despite the fact that DAS is a simpler storage device, it will cope with the absolute majority of data storage tasks just as well as a NAS server. At the same time, it has an attractive price with many really useful functions.

DAS CFI B8253JDGG + router: personal cloud storage

Equipping your CFI B8253JDGG DAS drive with personal cloud storage is as easy as shelling pears. All it takes is a decent router with support for host devices. Connect the DAS CFI B8253JDGG DAS storage to the router and access your home collection of movies, music and photos from anywhere, any time of the day or night, free of charge and without registration.

Create your own cloud storage, in the reliability of which you will be completely sure, and the volume of which will depend only on your needs. Five slots for hard drives over three terabytes with automatic RAID creation and background rebuilding of the array - no Google Drive will do this.

An external RAID DAS drive is an easier replacement for an expensive NAS server, providing you with reliable and convenient storage of your important information.

The characteristics of the DAS drive CFI B8253JDGG are presented in the table below.

DAS storage characteristics	CFI B8253JDGG
Type of equipment	External box for 3.5 "hard drives
Indicators	Power, activity, status (for each of 5 HDDs)
Supported RAID levels	5, 3, 10, 1, 0, JBOD
Chip	JMicron JMB394, JMB320 and JMS539
Interface	USB 3.0 (USB 2.0 compatible), eSATA
Control	Rear panel switches
Interface bandwidth	5000 Mbps (Super-Speed), 480 Mbps (High-Speed)., 300 Mbps when connected to eSATA connector
Possibilities	Automatic array rebuilding in RAID10 / 3/5 mode, background array rebuilding, hardware RAID platform
Cooling	1 fan 120 x 120 mm
# Of bays for HDD	5
Supported HDD interface	SATA 6Gb / s, SATA-II, SATA / 150
Large HDD support	Supports disks over 3 TB
Drive format	3.5"
The weight	4.2 kg

DAS CFI B8253JDGG + computer: back up valuable data

Gone are the days when the family archive was stored in a couple of albums in a dusty mezzanine. The modern home storage of photos, videos of celebrations and holidays and other memories dear to the heart is DAS connected to a computer or laptop. The footprint it occupies is negligible compared to the tens of terabytes of information you can take without noise and dust for years.

Storing valuable data on a laptop is convenient, but unsafe. A collection of your favorite movies or photos can be irretrievably lost if the drive fails, and valuable working information will disappear forever along with the laptop itself in the event of a breakdown or theft of the latter. To ensure that your work and personal information is always safe and sound, you need to back up your data (backup). Is always.

With the CFI B8253JDGG DAS drive, your data is protected - always. Thanks to the automatic building of a RAID array, you can always duplicate information from your computer or laptop drives to DAS, in the disks of which, in turn, the information will also be duplicated on several disks. Supported formats RAID 5, 3, 10, 1, 0 and JBOD allow you to create a fast, reliable or very reliable array, and restore all your business and personal information even if several hard drives fail.

CFI B8253JDGG + NAS: The Affordable Way to Double Your NAS Capacity

The CFI B8253JDGG external box is the most cost effective way to expand the available storage space for your server, workstation and NAS. Sooner or later, the capacity of the existing file server or media storage will not be enough, and you will have two options: buy a second NAS for a lot of money or expand the volume of the existing server with a DAS drive. Of course, it is better to choose the second option.

One or more DAS drives connected to the NAS server can significantly increase its usable volume. At the same time, DAS CFI B8253JDGG will be endowed with the full functionality of the existing NAS server: access from mobile devices, downloading files without a computer, and much more, depending on the capabilities of the NAS. By connecting a 5-disk DAS CFI to a single-disk NAS server, you will have a 6-disk NAS at your disposal, available to all users of your network. When connected via the high-speed eSATA port, access to the external DAS CFI module will be as close as possible to the access speed of the NAS's built-in hard disk.

When the task of backing up a multi-disk network storage, network video recorder (NVR) or a server, for example, 5 to 8 hard drives, appears, the problem of purchasing proportional capacity automatically arises. With a head-on approach, the decision is equal to buying a second NAS (NVR) for 5 - 8 disks. Which is really expensive. And here DAS CFI comes to the rescue, which with equal 5 disks is half the price of a 5-disk NAS.

Simply connect the CFI B8253JDGG External RAID Drive to any NAS via eSATA or USB, insert hard drives, select a storage mode and turn the B8253JDGG into action. Simplicity of settings, the ability to quickly "hot swap" drives and versatility of connection make the external RAID containers CFI B8253JDGG a reliable storage for your information. And the low price will make enterprise-grade reliability available to all private users.

Freelancer and real designer working storage

DAS storage CFI B8253JDGG is not only reliable, but also very fast. Equipped with USB 3.0 and eSATA ports, CFI B8253JDGG delivers blazing fast transfer speeds when connected to a PC or laptop. The speed of data exchange between the computer and the external USB 3.0 drive CFI B8253JDGG connected to it exceeds 200MB / s.

This is more than enough for a quick backup of layouts, transferring footage from a wedding for subsequent editing, or for replicating a catalog on several hard drives at once. ideal for productive work with a large amount of information, for example, for video editing, printing and industrial design.

To access multiple storage HDDs at the same time from a PC, server or NAS storage, you just need to set the CFI drive to CLEAN mode and connect it to the host device, changing the necessary disks as needed.

Contents I. Definition of DAS.
II. Distributed antenna system.
2.1. General diagram of the DAS network infrastructure and its types.
2.2. Passive RAS.
2.3. Active RAS.
2.4. Stages of the design of the RAS.
2.5. Radio plan preparation.
ІІI. Technical description of PAC components
3.1. PAC control rack
3.2. Diagram of connecting the BTS to the MA rack
3.3. Radio remote modules.
3.4. Optical components.
3.5. Indoor antennas.
3.6. Coaxial RF cable.
3.7. Splitter symmetrical / asymmetrical.
3.8. Jumpers are radio frequency.
3.9. Measurements of radio parameters of a built indoor network.

I. Definition of DAS

Distributed Antenna System (DAS).
It is a network with spatially separated
antennas connected to a common signal source
through the transport medium, which is most often
protruding fiber optic cable (FOC).

II. Distributed Antenna System

DAS Distributed Antenna System

2.1 General diagram of DAS network infrastructure and its types.

DAS system solution providers: Mobile Access, Commscope,
Powerwave, Corning, Zinwave, and many more.

2.2 Passive distributed antenna system.

Definition:
Passive DAS is built on the basis of cable networks.
- Advantages of passive DAS
The absence of additional noise or intermodulation interference in the system allows
implement a multichannel mode of operation without any degradation of services due to the possible
interference.
- Disadvantages of passive DAS
● Substantial costs for laying large diameter coaxial cables.
● Small size of coverage provided due to attenuation in coaxial cables.
● The maximum distance of the antenna from the signal source cannot exceed several hundred meters.
● Problems with scaling the system due to the dependence of coverage quality on length
cable communication lines. With long cable lengths, signal attenuation leads to zones
uncertain reception.
● Lack of performance monitoring: if any antenna starts to malfunction,
the operator finds out about this only after complaints from subscribers.

2.3 Active distributed antenna system.

Definition:
Active DAS is built according to the scheme of using radio remote
modules united by one controller using optical
lines.

2.3.1 Active distributed antenna system.

Benefits of active DAS
● Large realizable indo-coverage area due to the longer length of fiber-optic lines
communication.
guaranteed signal level at the output of each antenna, regardless of its distance from the entry point.
the ability to remotely monitor and control each specific antenna allows you to localize
emerging problems with the quality of communication.
no interference between antennas.
easy scaling - easy to increase coverage and capacity.
no restrictions on the number of installed antennas - since each antenna is an extension
only one signal source, no need to configure each antenna for a specific location
installations.

2.4 Stages of PAC design.

The order of the design steps for a distributed antenna system:
Obtaining technical requirements for the system;
Obtaining floor plans;
Obtaining technical requirements from the operator to connect to the system;
Creation of technical specifications for planning and design;
Selection of the system equipment supplier;
Calculation of the configuration and the required capacity of the system to ensure high-quality communication
according to the technical requirements of the customer;
Dividing the structure into coverage sectors, planning and system design
distributed antennas and cable infrastructure;
Preparation of a working project;
Equipment installation;
Commissioning;
Connecting the operator, launching and putting the system into operation;

10. 2.5 Stage of preparation of the radio plan.

An example of preparing a radio plan using specialized software:

11. III. PAC Technical Description

Active and passive components of the RAS

12. 3.1 Rack for control of the distributed antenna system.

Communication control rack configuration:
The main control module of the RAS system is located in the technical room;
The module consists of 1 rack 19 ”and can be configured in height depending on
complete set of indoor units;
Maximum power consumption 400W;
Power supply type - DC 60V;

Stand weight no more than 100kg.
Optical patch cords are connected to the module, which connect it to the
radio modules through an optical distribution frame;
Operator base stations are connected to the module according to the scheme consisting of a coaxial cable,
addition bridge, symmetric / asymmetric dividers, loads.

13. 3.2 Scheme of connecting the operator's BS to the control rack.

An example of connecting the BTS to the control rack of the RAS

14. 3.3 Remote radio modules

indoor radio module
outdoor radio module
MobileAccess MA HX Remote Unit:
The remote unit of the radio module is usually located
on the floors of the building (does not require special
adapted premises;
Internal and external cabinet versions;
Power consumption no more than 350W;
Types of types of power supply - DC 75V or AC -90… 264B;
Working temperature +0 ... + 50˚C;
The weight of the rack is not more than 32kg. indoor unit /
52 kg. external block.
An optical cable is connected to the module for
integration with the main control module;
The remote module connects to the antennas using
jumpers and coaxial cable.

15.3.4 Optical components

16. 3.4.1 Optical components

Internal and external appearance of optical components:
On the left is the image of the optical cross-country view from the inside;
Top image SC / APC fiber patch cord;

17.3.5 Antennas used in indoor solutions

Kathrein 800 10748
Kathrein 800 10465
MARS MA CL67-15
Kathrein 738 448
Basic type of indoor antennas
Indoor antenna mounting technique

18. 3.6 RF Coaxial Cable / Connectors.

Reliable coaxial connection
cables - the secret of successful deployment of communication systems
Key to good wireless performance
include the quality and reliability of the installation of connectors on the lines
transmissions using coaxial cables.
It is natural to assume that the more difficult the installation of connectors,
the less the probability of their correct installation, and this, in its
turn has an adverse effect on quality and
reliability of the entire system.

19. 3.7 Symmetrical and asymmetrical splitters.

Asymmetric splitter / taper
Symmetric splitter

20.38 RF jumper

Jumpers are used to connect antennas with a cable / cable with a splitter / radio module with a cable.

21. 3.9 Measurements of the built indoor network.

- Testing the quality of the radio network coverage
- Measuring the parameters of the quality of service provision
- Testing the quality of additional services (VAS) in mobile networks
- Measurement of quality parameters of data transmission services in radio networks
- Measurement of parameters of the quality of voice transmission services in radio networks

22.

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Welcome to the HP Storage Site!
This is the first blog post on the site. In it, I will talk about the classification of storage systems used in modern computer systems.
All storage systems are divided into three large groups: DAS, NAS and SAN.
Let's consider each group in detail.

DAS- Direct Attached Storage is a solution where a storage device is attached directly to a server or workstation without using a storage network. Literally translated "Direct Attached Storage" means "directly attached storage". For connection, an HBA (Host Bus Adapter) is used - a device installed or built into a server or workstation.
The protocols used to connect DAS are ATA, SATA, eSATA, SCSI, SAS, and Fiber Channel.

NAS- Network-attached storage is a storage system that provides clients with file access and is connected to the network. Network-attached storage is translated as "network attached storage". NAS can be used not only as a file server, but its software and hardware components are specially selected and tested to fulfill the role of a file server. Clients usually connect to the server over a public Ethernet network. NAS systems typically contain one or more hard drives, often organized into logical, redundant storage groups or RAID arrays. NAS - Network Attached Storage removes responsibility for the safety and access to files from other servers on the network. File access is usually provided over network protocols such as NFS (Network File System), SMB / CIFS (Server Message Block / Common Internet File System), or AFP (Apple Filing Protocol).

SAN- The storage area network is a dedicated network that provides access to consolidated, block-based storage systems. Storage area network is translated as "storage area network". SANs are mainly used to make storage devices such as disk arrays, tape libraries, available to servers as if they were connected directly to the servers. Typically, a SAN is a network of storage devices that are not accessible over a shared LAN. Since 2000, the cost and complexity of SANs have dropped to levels that can be widely deployed even in small and medium-sized businesses.
SAN provides no abstraction, only block operations. This means that access to the storage system via NFS, SMB / CIFS, or AFP is possible only through a dedicated gateway server.