Excess production of flash memory has led to a significant reduction in prices for solid-state drives this year. As a result, SSD drives, which were considered luxury for another 5 years, became available to the mass consumer. For those who did not have time to get acquainted with the capabilities of SSD, in this material we described in detail what a solid-state drive is. A comparison of the capabilities of SSD and HDD will allow you to decide on a purchase, and also to choose the optimal type of media for a specific task.
Varieties of disks, what is SSD, HDD, and SSHD
To store information in computers, laptops, and servers, one or more types of storage devices are used:
- Solid State Drive – SSD.
- Hard disk – HDD.
- The hybrid drive is SSHD.
Solid-state drive in translation from English solid-state drive is not a mechanical disk, built on memory chips. Chips for storing the information are soldered on a printed circuit board, together with a controller and an additional buffer for caching data.
Typically, the finished device fits in a standard 2.5-inch case. Thanks to this, SSD drives are compatible with most laptops and PCs. More compact versions of the format are also widespread: mSATA and m2. The latter format, thanks to its compact dimensions of 80x22x3.8 mm and weight of 6.3 grams, for example, the AP120GAST280 model, has taken root in ultra-thin laptops. For comparison, the dimensions of the 2.5-inch HDD / SSD are 100x70x7 mm. The maximum capacity of modern SSD drives is 4 TB.
HDD – hard disk drive, is a mechanical device for storing data. In colloquial speech, it is sometimes referred to as a hard drive. The disc works on the principle of magnetic recording. Data is stored on plates, which usually rotate at a speed of 5900 or 7200 rpm. Writing and reading is performed by a read head, which moves over the disk, but does not touch the surface. Large capacity drives typically use several thin plates and read heads.
Hard drives are available in two versions 2.5 and 3.5 inches. 2.5-inch drives are commonly used on portable systems and laptops. 3.5-inch drives are often installed in the PC and server chassis. The maximum disk capacity is 5 and 14 TB, for 2.5 and 3.5 inches, respectively.
Hybrid drive in translation from English solid-state hybrid drive is a combined SSD and HDD drive. Typically, these are two separate devices in one case or a regular hard drive with additionally soldered memory on the control board. The part with the HDD is used to store basic information, and part of the SSD is used to speed up data transfer. The main goal of the appearance of such drives is to accelerate the work of ordinary hard drives.
Disks are also available in 2.5 and 3.5-inch form factors. The maximum disk size is 2 and 16 TB, for the younger and older versions, respectively. Additionally, a certain amount of flash memory is installed, for example, Seagate drives use 8 GB of MLS memory.
Distinctive features of SSD, HDD, and SSHD
SSD, HDD and SSHD drives are structurally different, as well as characterized by different data transfer speeds. Due to the absence of mechanical elements, the weight of a 4 TB SSD is 62 grams, while HDD counterparts of the same format weigh 190 grams, and 3.5-inch HDD / SSHD models weigh 490 grams. In the form factor m.2, the weight and dimensions are even smaller, which allows you to create compact assemblies or integrate drives into ultra-thin laptops.
The speed of writing and reading information in SSDs is up to 6 times higher compared to HDDs, while m2 has an even higher rate. For example, the data transfer rate of the average SSD is 400-550 MB per second, in m2 drives 2000-4000 MB, and in the HDD on average 100 MB.
High-speed SSD is achieved due to the lack of mechanical parts in the structure, and the work of the moving elements is assigned to the controller. In the process of recording, information is placed in the corresponding blocks of flash memory. The controller marks the occupied blocks in the table, so it quickly calculates the location of this or that information when reading. And the presence of additional DRAM memory for caching data allows you to store frequently used information in a buffer, which improves performance.
2.5-inch SSD disks on average provide information transfer at speeds up to 550 MB, which is explained by the limitation of the SATA 3 interface to 600 MB. SSD m.2 format drives are connected via the PCI Express connector, where there are more bus lines and, accordingly, higher data transfer speeds. For example, 4 PCI-E 2.0 lines provide read/write speeds of 2000 MB, and 4 PCI-E 3.0 lines provide 3940 MB.
The speed of the hard drive is tied to the speed of the spindle, which rotates the magnetic disk. In conventional disks – 5900-7200 rpm, which provides a read / write speed of 90-120 MB. In server disks, the spindle speed is 10,000-15,000 rpm, which allows reaching 300 MB, but the price of such drives is 8-10 times higher. In this case, the real speed is 2-3 times less, which is explained by the peculiarity of the disk.
The area of the magnetic disk consists of ring tracks divided into equal sectors. To write or read information, a reading head is used, which moves along the annular tracks of a rotating disk. If a request is received to read certain information, the disk calculates the location of the data and then moves the magnetic block to the desired track. Next, the magnetic unit waits for the track to move and reads the information. If the data is stored on several tracks, the procedure is repeated, which affects the access time.
Hybrid drives are faster than conventional hard drives, due to the presence of fast flash memory. Important and frequently used information is placed on the solid-state partition, while the main data is stored in the magnetic disks of the HDD. For example, if a disk is used as a system disk, files critical for the OS are written to flash memory, which speeds up system startup. The increase in normal writing and reading is approximately 15%.
However, the use of SSHD is justified only in some specific scenarios. For home use, it is more profitable to use a bunch of regular SSD and HDD.
Advantages and disadvantages of SSD compared to HDD
Solid State Strengths:
- High data rate. When connected via SATA, the read / write advantage is up to 6 times, while using PCI-E up to 40 times. Thanks to this, the launch of the system, games and programs is several times faster.
- High IOPS – I / O. The advantage when working with data from 86 times, which noticeably affects when using the swap file.
- Lack of mechanical parts. Without moving parts, the disc does not make noise or crackle. There is no heating, which eliminates the need for a cooling system. Exception m.2 drives that heat up under heavy load.
- Overload resistance. Dropping, bumping, or shaking does not usually affect disk performance.
- Compact dimensions and weight. Allows you to assemble compact assemblies or install in thin laptops.
- High price. 1 TB is on average 2.5-14 times more expensive.
- Low resource of work. The amount of overwriting is affected by the type of memory. For example, Kingston SA400S37 / 960G with a capacity of 960 GB with ordinary TLS memory allows you to overwrite a total of 300 TB. By comparison, the Seagate Skyhawk Series HDDs can withstand an annual rewriting of 180 TB and are able to work stably up to 10 years or more.
- The need for cooling m.2 drives. The transfer is given at a speed of 800-1000 MB and frequent access to the drive contributes to heating up to 70 degrees. Therefore, to remove excess heat, you need to take care of additional cooling.
- The probability of data loss with prolonged inactivity of the drive is 6-12 months.
- Voltage drops can completely disable the drive without the possibility of recovery. If the electronic part burns out due to a short circuit, data recovery will not work. In hard drives, usually only the control board burns out, and the magnetic disks remain intact, which simplifies the process of recovering information.
What to choose
Modern SSDs demonstrate a high level of MTBF, but so far they are not able to compare in this indicator with hard drives, which have been working stably for years and decades under high load. Therefore, you should not be afraid to buy an SSD drive. Another thing is that the cost with the same volume of solid-state media is at least 2 times higher. Therefore, such drives are not suitable for downloading torrents or storing various information. But to install the operating system, games and specialized programs, the purchase of an SSD is quite justified, since it will reduce the waiting time by 3-5 times.
Winchesters, in view of the relative cheapness and reliability, are better suited for storing voluminous information, downloading torrents and regularly rewriting, for example, in DVRs. Therefore, when assembling a personal computer, it is better to install a pair of SSD and HDD. In laptops, it is also wise to use a solid-state drive, and other information is best stored on an external drive.
Buying a hybrid drive makes no sense because of the high cost – 2 TB SSHD equals 4 TB HDD. The exception is the use of the drive-in workstations, work in specialized applications.
If you intend to speed up your computer or laptop, then you should add an SSD. Using a solid-state drive will accelerate the launch of the operating system, increase the load of games and programs. At the same time, a complete transition to such storage media is impossible, due to the high cost and rapid wear and tear with constant rewriting. Therefore, to speed up the system and applications, it is better to use SSD, and store information on the HDD.