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Which is the best hard drive ssd or sshd. Why is a hybrid drive better than HDD and SSD? Disadvantages of hybrid hard drives

January 19, 2014 at 05:07 PM

SSHD Hybrid Disks - What kind of bird?

King Servers corporate blog

In our work, we often have to deal with a variety of storage media, including hard drives and solid-state storage media. At the same time, sometimes quite unusual devices that are not common everywhere come across. For example, SSHD are hybrid hard drives. Probably, on Habré there are people who are well acquainted with this type of information storage, but there are also those who have not even heard of such "hybrids".

So, hybrid hard drives are, first of all, a compromise solution that allows both to increase the overall performance of the system in which they are installed and to reduce the price of such a system.

After all, despite the widespread use, solid-state drives are still quite expensive, and it is unlikely that the moment will come soon when the price of such drives will drop significantly.

Regular hard drives- inexpensive, for the most part, but their performance is limited, you cannot "jump" above a certain limit. Therefore, hybrid hard drives appeared. SSHDs appeared a few years ago, and at first they were pure exotic, which few people took seriously (and few knew about them). The main advantage of the hybrid hard disk is an increase in the overall performance of the system in which they are installed using only one disk bay (and not two if using both an SSD and a conventional hard disk). Now there are models of "hybrids" of small sizes, for example, with a thickness of only 7 mm (this is exactly the model ST500LM000 from Seagate), which allows installing such drives in netbooks / ultrabooks.

The principle of operation of SSHD is based on caching the most frequently used data using flash memory, that is, the SSD part of the "hybrid". Already at the first start operating system on a laptop / PC with a "hybrid", the non-volatile part of the SSHD memory contains the files that the operating system needs to boot. As a result, the OS startup speed increases, and quite significantly.

The hybrid drive, by the way, shows almost the same results in file transfer speed compared to conventional hard drives. But the difference is in work different types devices becomes very noticeable when comparing the access time to files (Access Time). For example, if you take Seagate drive ST500LT032 with a capacity of 500 GB and compare with the ST500LM000 "hybrid" of the same capacity, the speed of access to files will be 24.2 and 0.3 ms.

As for the maximum interface speed, the difference is no longer several times, but 15%. In the first case, 101 MB / s, in the second - 115 MB / s.

There are also disadvantages, and first of all, this is the inability to fit all critical data on the SSD part of the SSHD disk. Usually, a hybrid SSD is installed with a capacity of 8 GB, sometimes more (for example, models with 32 GB of flash memory are not uncommon), but then such a disk will be more expensive.

At the price of "hybrids" only slightly exceed the price of conventional hard drives... If we take the models already mentioned above, the price of the Seagate Laptop Thin SSHD ST500LM000 is $ 73-75, and the Seagate ST500LT032 is about $ 50.

So, if you want to increase your OS boot speed, as well as the overall performance of your laptop / desktop PC, we recommend using "hybrids". Well, that's in case savings are important to you. If not, then you should use SSD and conventional hard drives separately.

After all, despite the widespread use, solid-state drives are still quite expensive, and it is unlikely that the moment will come soon when the price of such drives will drop significantly.

Conventional hard drives are inexpensive, for the most part, but their performance is limited, you cannot "jump" above a certain limit. Therefore, hybrid hard drives appeared. SSHDs appeared several years ago, and at first they were pure exoticism, which few people took seriously (and few knew about them). The main benefit of a hybrid hard drive is to increase the overall performance of the system in which they are installed using just one drive bay (rather than two if using both an SSD and a conventional hard drive). Now there are models of "hybrids" of small sizes, for example, with a thickness of only 7 mm (this is exactly the model ST500LM000 from Seagate), which allows installing such drives in netbooks / ultrabooks.

The principle of operation of SSHD is based on caching the most frequently used data using flash memory, that is, the SSD part of the "hybrid". Already at the first start of the operating system on a laptop / PC with a "hybrid", files that the operating system needs to boot are placed in the non-volatile part of the SSHD memory. As a result, the OS startup speed increases, and quite significantly.

The hybrid drive, by the way, shows almost the same results in file transfer speed compared to conventional hard drives. But the difference in the operation of different types of devices becomes very noticeable when comparing the access time to files (Access Time). For example, if you take a 500 GB Seagate ST500LT032 disk and compare it with the ST500LM000 hybrid of the same capacity, the file access speed will be 24.2 and 0.3 ms.

As for the maximum interface speed, the difference is no longer several times, but 15%. In the first case, 101 MB / s, in the second - 115 MB / s.

At the price of "hybrids" only slightly exceed the price of conventional hard drives. If we take the models already mentioned above, the price of the Seagate Laptop Thin SSHD ST500LM000 is $ 73-75, and the Seagate ST500LT032 is about $ 50.

Man doesn't know what a hybrid is HDD... The fashion for combining several fundamentally different technologies in a single device not new.

For example, cars that selectively use a traditional combustion engine or electric drive for movement have become commonplace. This solution makes it possible to get by with "little blood" in the gradual transfer of technology to a new alternative. Hybrid hard drives fully comply with this rule... Let's take a closer look at this issue.

Retired ... or more alive than all the living?

Currently, in the field of computer technology, the main device for long-term storage of information is a hard disk or hard drive (HDD). Its design and operating principle are quite simple: in a small metal case several disks made of non-conductive electricity material. On all sides, the surface of each of them is covered with a sprayed magnetic layer. The discs are strung on a common spindle axis rotated by an electric motor at a constant speed (in some models it can change stepwise, depending on the intensity of use). A special mechanism moves the frame with the read / write heads over each side.

When writing, parts of the surface are magnetized, and when reading, the opposite process occurs - magnetic field a current is induced and converted by the controller into a data stream. Over the decades, the technology has been tested, "childhood diseases" have been eliminated.

A dark horse

However, with the advent of solid-state memory, alternative solutions, in which there are no rotating parts, and the recording is carried out by changing the position of the floating gate in the transistor. Such drives are called SSD (from the English. Many believe that based on solid-state memory cells, the performance of which is significantly higher than the work of HDDs, they will gradually replace classic hard drives. It is too early to talk about a global transition (despite the fact that there are hybrid HDDs). And here's why :

The cost of one gigabyte of disk space for an SSD is several times higher than that for an HDD (the coefficient can be obtained by dividing the price by capacity);

Reliability is not so simple, everyone solid state drive characterized by the permissible number of write / read cycles;

The technology is too new, it is constantly being improved, so yesterday the device purchased today may be hopelessly outdated (take at least the support of the TRIM team).

Hybrid hard drive

Realizing that it is too early to talk about a complete change of technologies, manufacturers have proposed a compromise option that combines HDD and SDD. The design of such a device is based on magnetic disks (a hard drive with its low cost and ... not too impressive performance). The peculiarity is that the hybrid hard drive also contains chips and an SSD controller. Of course, there is no need to talk about hundreds of gigabytes, usually the volume is limited to ten. That is, the main volume falls on magnetic disks (for example, 750 GB), the capacity of the SSD is 8 GB, and, of course, the cache (32-64 MB). During operation, hybrid copies the most requested data into fast solid-state memory, then working with it. In other words, the SSD in this solution is a L2 cache.

Why Choose a Hybrid Hard Drive Over SSD
A hybrid hard drive combines the performance of a solid state drive with the capacity of a mechanical drive. They more SSD and faster than a simple hard drive.
It is sometimes referred to as a Solid State Hybrid Drive (SSHD). The drive automatically caches data to the solid state storage device, providing increased speed access to files.
Solid-state drives are much faster than mechanical drives. Prices have dropped markedly, so it makes sense to upgrade to an SSD. But even cheaper disks are less capacious. A 1GB solid state drive costs $ 0.58 and a gigabyte mechanical drive costs $ 0.06. A reasonable price solid state drive has a maximum capacity of 256GB, while a mechanical drive has a capacity of 2TB or 3TB. Mechanical drives are slow, but they have enormous storage capacities at an extremely low cost per gigabyte.
To take advantage of both types of drives, many equip computers with solid state drives and mechanical drives at the same time. The solid state drive is used for system files and programs that need speed. Large mechanical disk is used for long-term storage of files that are not particularly needed fast access, - for example, a collection of films. This requires you to install both disks on your computer and choose which programs and files to place on each disk. You have to move files to another disk yourself. Moving a program to another drive means removing it and reinstalling it in a different location.
The hybrid drive contains magnetic disk and a solid state drive with a volume of a small solid state drive. This disk appears to the operating system as a single disk. You are not responsible for which files go to the mechanical drive and which to the solid state drive. The drive's firmware determines what gets to the solid state drive and what doesn't.
The SSD part of the disk serves as a "cache" - files that are often accessed - files of the operating system and programs, the firmware stores in the SSD drive. The cache is stored in nonvolatile semiconductor solid-state memory, surviving reboots and thus speeding up the boot procedure.
Access to system and program files produced at the speed of a solid-state drive, while providing the capacity of the magnetic drive for other files. The disk handles this on its own - you don't have to move files back and forth or decide what to put where.
Most hybrid drives have SSD storage small. Some of them have 1 TB of mechanical capacity and only 8 GB of semiconductor memory. 8 GB is enough for storing system files and programs, but this volume is incomparable with 128 or 256 GB, which can accommodate all system and program files.
Apple's Fusion Drive is also hybrid and has 1TB to 3TB of magnetic storage along with 128GB of solid-state storage.
Hybrid drives are cheaper than solid-state drives because they contain less solid-state memory. A 2TB hybrid drive with 8GB of cache is more expensive than a conventional 2TB mechanical drive, but cheaper than a 256GB solid state drive with even less free space.
The big advantage is that a hybrid drive is a single physical drive. If your laptop only has room for one drive, but you need the speed of a solid state drive and the capacity of a mechanical drive, then a hybrid drive is the way to go.
It's all about price and capacity. If magnetic and solid state drives were the same in cost, hybrid drives would not be needed at all. Solid state drives would be better in every way.
The hybrid drive is slow on first use. When he first starts working, caching has not yet been performed, which means that the disk will be as slow as a classic magnetic one. As you use it, the drive will figure out which files to cache and the speed will gradually increase.
It's up to you to choose which drive to use, but our team prefers a hybrid drive with at least 32GB of solid-state memory.

Today there are a large number of different types of devices for recording, storing and processing information. One of the most demanded developments, which have already quite densely entered our life, is a hybrid SSHD device.

It is a normal hard drive equipped with a solid-state memory section. Operating principle this device peculiar.

History

The device of this type appeared relatively long ago, almost immediately after various kinds of solid-state drives such as SSD were put into mass production. The latter had extremely high performance and other advantages.... But they also differed in almost exorbitant cost relative to conventional hard drives.

Photo: world's first transparent SSD

The way out of this situation was a hybrid hard drive. He, unlike his more simply arranged counterparts, is supplied not only with ordinary pancakes rotating on a special spindle, but also with a memory chip.

So peculiar engineering solution- combine two different types memory in one case - allowed to reduce the cost of computers and at the same time increase their performance.

In order to understand what this SSHD is, you need to familiarize yourself with its device. The most important difference from a conventional hard drive is the presence of memory chips.

Device

The considered type of device for storing and processing data consists of two main parts:

Solid state memory;

Hard drives.

Hard drives can be made of aluminum or glass plates coated with some kind of ferrimagnetic material. Solid-state memory is a microcircuit, data recording on it is carried out in a non-mechanical way.

The plates, rotating on a special spindle, are placed in a hermetically sealed chamber filled with nitrogen or other similar gas. It is free of impurities, its moisture content is minimal. There is a double cleaning system in case dust or other foreign particles get into the containment. There is a three-phase synchronous motor inside the case, as well as heads for reading and writing data.

Principle of operation

The principle of operation of an SSHD device is very simple. Arrays for recording data are ordinary metal disks with a special coating. Information is recorded on them using the tunnel magnetoresistive effect. As a result of this effect, the magnetic field affects the resistance of the magnetic surface of the disks. Which leads to a change in the magnetization vector of individual elements.

Data reading is carried out in the same way. The head hovers over the metal surface and the opposite process occurs - the surface resistance of the plates affects the magnetic field of the writing head. The information received is analyzed and deciphered.

The principle of operation of a hybrid drive is completely different from a conventional hard drive. In fact, this microcircuit is a flash memory into which various kinds of data are written. Its speed is much higher than that of a standard hard drive.

The essence of the hybrid SSHD is that metal plates are used to house permanently stored information. The use of the solid-state part of the device is carried out only after the launch of the operating system. The files that the system constantly accesses are written to it. Thus, access to them is greatly simplified and accelerated.

It is due to this that the speed of work increases. An interface called SATA is used as an interface for connection.

Performance

If you compare the file transfer speed of a conventional drive and a hybrid, it will be almost the same. In SSHD it will be slightly faster, the speed gain due to solid-state memory will be a maximum of 15%. But the difference becomes very noticeable when you measure the speed of file access. This parameter is referred to as Access Time in all testing applications.

The two most common models can be used for comparison:

Data access speed when using ST500LT will be 24.2 m / s. The ST500LM has a similar characteristic of 0.3 m / s. Thus, the performance difference is very large.

Most clearly, you can see the difference in performance when testing in any specialized work... For example, in PCMark 05.

Where is the best place to use an SSHD drive?

The drives in question are used both in laptops and in ordinary ones, stationary computers... That is why both a full-format version - 3.5 inches and a reduced version are available. There are also a large number of models, the thickness of which is within 7 mm. Therefore, they are often used in laptops.

Most often, drives with solid-state additional memory are used in laptops, since these devices suffer from a lack of performance. This is due to the compactness of the hardware. And a solid-state drive can compensate for this disadvantage. But you can also often find the drive in question in ordinary desktop PCs.

Short review

Most often on sale you can find a model marked as Seagate Laptop Thin SSHD... You can also easily find its overview, by appearance you can confuse it with the most common disk drive equipped with two metal plates coated with ferromagnetic sputtering.

The considered model has dimensions 2.5 inches. The data exchange process is carried out via an interface labeled SATA 6. Scope internal memory is 500 GB. The spindle speed is not very high - only 5400 rpm.

Other performance characteristics are also outstanding:

power consumption - 0.9 W;
the level of the emitted noise - 2.2 dB;
impact resistance - 350/1000 g;
dimensions:

length - 100.35 mm;
height - 70.1 mm;
depth - 7 mm;

weight - 95 g.

Compact size, durability and low power consumption make the drive in question simply irreplaceable when assembling the latest generation notebooks. It allows you to significantly increase productivity and reduce the total weight.

A full transition to hybrid and solid-state storage will take place shortly. Since this direction has a very great potential for development.

The extremely high operating speed allows for large quantity operations in the shortest period of time. Solid state read-only memory is a big step into a new future.