Placement
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External. Hard drives designed to be used as external removable devices. They are carried out in separate protected cases, often they are powered from an external source; are designed to be plugged in and out regularly and are well suited for transporting large amounts of information between computers. The most popular way to connect such drives is USB, but there are other options (for more details, see "Connection interfaces")
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Internal. Hard drives designed to be installed inside a computer or laptop case and permanently function as an element of a computer system. They do not involve frequent reconnection — technically it is possible, but much more problematic than in the case of external drives. Most often they are connected via the SATA interface of one version or another (see "Connection interfaces"), other options are relatively rare, mainly among professional models.
Size
Rated capacity is one of the key parameters of a hard drive, which determines how much information can fit on it. For SSHD, this item indicates the capacity of only the hard drive, for RAID arrays, the total capacity of the array.
The volume of information in the modern world is constantly growing and require more and more capacious drives. So in most cases it makes sense to choose a larger disk. In fact, the question of choosing this parameter often rests only on the price: the cost of the drive directly depends on the volume.
If the question is in such a way that you need to choose a disk "smaller and cheaper, but that's enough" — it's worth evaluating the amount of information that you have to deal with and the specifics of use. For example, for an ordinary office PC, designed mainly for working with documents, an internal drive of
2 TB and even
1 TB will be more than enough, and an enthusiastic gamer will need
4 TB,
6 TB and even
8 TB will not be superfluous. If you use a disc for recording from camcorders, then you can get
a 10 TB,
12 TB,
14 TB,
16 TB,
18 TB or more HDD.
Connection
— SATA. Nowadays, it is the most popular interface for connecting internal hard drives.
the first version of SATA provides a data transfer speed of about 1.2 Gbit/s,
SATA 2 has a practical data transfer speed of about 2.4 Gbit/s (300 MB/s), and the most advanced generation
of SATA 3 has a speed of 4.8 Gbit/s (600 MB/s)
- eSATA. Modification of the SATA interface designed for connecting external hard drives; not compatible with internal SATA. Practical data transfer speed is similar to SATA 2 and is about 2.4 Gbps (300 MB/s).
- SAS. Modification of the SCSI interface provides data transfer speeds up to 6 Gbit/s (750 Mb/s). It is used mainly in servers; it is practically never used in desktop PCs and laptops.
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USB 2.0. The earliest of the USB standards found in modern hard drives - and exclusively external ones (see “Execution”). Provides connection to a traditional full-size USB port, provides data transfer speeds of up to 480 Mbit/s, as well as fairly low power supply, which is why drives with this type of connection often require additional power. In light of all this, as well as the emergence of the more advanced USB 3.2 standard (see below), today USB 2.0 is considered obsolete and is extremely rare, mainly in inexpensive and early models of drives. However, a disk with this interface can also be connected to a n
...ewer USB port - the main thing is that the connectors match.
— USB 3.2 gen1(previous names USB 3.1 gen1 and USB 3.0). A standard for connecting external HDDs, which replaced the USB 2.0 described above. Uses a traditional full-size USB connector, provides data transfer speeds of up to 4.8 Gbps (600 MB/s), as well as higher power supply, making it easier to do without external power in such drives. However, for the same reason, you need to be careful when connecting USB 3.2 gen1 drives to older USB 2.0 connectors - such a connector may not have enough power to power a newer drive.
- USB 3.2 gen2. Further development of the USB 3.2 standard (previously known as USB 3.1 gen2 and USB 3.1). The maximum data transfer rate in this version has been increased to 10 Gbps, and the power supply can reach 100 W (with support for USB Power Delivery technology). At the same time, drives with this type of connection can also work with earlier versions of full-size USB connectors - the main thing is that there is enough power supply.
— USB C 3.2 gen1(previous names USB C 3.1 gen1 and USB C 3.0). Connection via USB C connector, corresponding to USB 3.2 gen1 capabilities. These capabilities are described in more detail above; the difference from the “regular” USB 3.2 gen1 in this case lies only in the type of connector: it is a relatively small (slightly larger than microUSB) socket, which also has a double-sided design. Thanks to its compact size, USB C is found both in full-size PCs and laptops, as well as in compact gadgets like smartphones and tablets; Some drives with this connection initially allow “mobile” use.
— USB C 3.2 gen2(previous names USB C 3.1 gen2 and USB C 3.1). Update and improvement of the USB C 3.2 gen1 described above - the same USB C connector and increased data transfer speed to 10 Gbps (as in the “regular” USB 3.2 gen2).
- Thunderbolt. High-speed interface for connecting external peripherals. It is used mainly in Apple computers and laptops, although it is also found in equipment from other manufacturers. Note that in modern HDDs there are mainly two versions of Thunderbolt, which differ not only in operating speed, but also in connector: Thunderbolt v2(up to 20 Gbps) uses a miniDisplayPort plug, and Thunderbolt v3(up to 40 Gbps) — USB C plug (see above). In light of this, some hard drives implement USB C and Thunderbolt connections through a single hardware connector, which automatically detects which computer input the device is connected to.Cache memory
The amount of internal hard drive memory. This memory is an intermediate link between the high-speed computer RAM and the relatively slow mechanics responsible for reading and writing information on disk platters. In particular, the buffer is used to store the most frequently requested data from the disk — thus, the access time to them is reduced.
Technically, the size of the buffer affects the speed of the hard drive — the larger the buffer, the faster the drive. However, this influence is rather insignificant, and at the level of human perception, a significant difference in performance is noticeable only when the buffer size of the two drives differs many times — for example,
8 MB and
64 MB.
Record technology
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CMR(Conventional Magnetic Recording) is a classic method of magnetic recording, characterized by high data access speed. CMR hard drives are used in systems where it is important to provide high (as far as possible) data read/write speed. These are user computers, security video surveillance systems, etc. The main disadvantage of CMR hard drives is the high complexity of creating volume drives, which is reflected in their price. Additionally, HDDs with CMR technology are quite “gluttonous” in terms of power supply.
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SMR(Shingled Magnetic Recording) — a promising technology for magnetic recording, which is called "tiled". SMR allows to achieve high data density, which in turn increases the capacity of memory drives and lowers their market value. SMR hard drives have slow rewriting speed, which makes such memory drives poorly suited for use in client computer systems. But they have proven themselves well when working as part of data processing centers, archives and similar systems for which low write / rewrite speed is not critical. However, some companies still produce SMR solutions for personal and even mobile systems. These HDDs use an optimized write/rewrite technology called Drive-Managed SMR (DM-SMR).
Plates
The number of platters provided in the design of the hard drive.
Physically, a hard disk consists of one or more platters, on which information is recorded. Several plates can be provided in order to achieve the desired volume without increasing the form factor. At the same time, it is also necessary to install an appropriate number of reading heads in such a drive, which complicates the design, reduces its reliability, and increases the cost. Therefore, manufacturers choose the number of plates based on a reasonable compromise between these points, and for selection, this parameter is more of a reference than practically significant.
Average search time
The time it takes for the hard disk mechanics to find random requested data to read. For each specific case, the search time is different, as it depends on the location of the data on the surface of the disk and the position of the read head, therefore, the average value is indicated in the characteristics of hard drives. The lower the average seek time, the faster the disk works, all other things being equal.
Shockproof
A parameter that determines the resistance of the hard drive to drops and shocks during operation (that is, in the on state). Shock resistance is measured in G — units of overload, 1 G corresponds to the usual force of gravity. The higher the G number, the more resistant the disc is to various kinds of concussions and the less likely it is to be damaged, say, in the event of a fall. This setting is especially important for external drives and drives used in laptops.
Reading noise level
The level of noise produced by the disk when reading and/or writing information. The source of sound in this case is the moving plates of the disk, as well as the mechanics that control the reading heads. The lower the noise level, the more comfortable the use of the device. The maximum noise produced by modern hard drives during operation is about 50 dB — this is comparable to the sound background in an average office.
