Features
The general purpose of a hard drive is the type of devices for which it was originally intended.
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For PC. Hard drives designed for use with conventional consumer computers and laptops. At the same time, the possibility of installing an internal HDD (see "Performance") directly depends on the form factor (see the relevant paragraph), while external models are not subject to such restrictions — it is enough for them to have the appropriate connection connector. Also note that almost all external hard drives are designed specifically for PCs; making server models external is not technically justified.
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For the server. Hard drives designed for servers have increased speed and reliability, because they constantly have to receive and give large amounts of information. To ensure speed, they may provide an increased rotation speed (up to 15,000 rpm). Such drives are made only internal (see "Performance"), and, in addition to SATA, they can use other, more specific connection methods — for example,
SAS(see "Connection interfaces").
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For game console. Specialized hard drives designed for use with game consoles. They are made only external (see "Performance"), they are intended mainly for storing games — including saves and user settings profiles. The main difference between such devices and classic external HDDs is
...precisely the optimization for working with game consoles, including the availability of special software tools for improved integration. Many of these drives are originally designed for a specific model or family of set-top boxes.Form factor
The form factor in which the hard drive is made.
This indicator determines primarily the size of the device. But its more specific meaning depends on the execution (see the relevant paragraph). So, in the case of external drives, only the overall dimensions of the case depend on the form factor, and then quite approximately. But internal HDDs are installed in slots with a well-defined size and location of holes for fasteners; these holes are made specifically for one form factor or another. For desktop PCs, the standard form factor is
3.5", for laptops —
2.5" ; at the same time, there has been a recent trend in desktops towards miniaturization and the transition to 2.5-inch drives. Theoretically, there is an even smaller form factor — 1.8", but in fact it is used mainly among ultra-compact external HDDs.
Interface
— SATA. Nowadays, it is the most popular interface for connecting internal hard drives.
the first version of SATA provides data transfer rates of about 1.2 Gbps,
SATA 2 has a practical data transfer rate of about 2.4 Gbps (300 MB / s), and the most advanced generation of
SATA 3 has a speed of 4.8 Gbps (600 Mbps)
eSATA. Modification of the SATA interface, designed to connect external hard drives; not compatible with internal SATA. The practical data transfer rate is similar to SATA 2 at about 2.4 Gbps (300 Mbps).
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USB 2.0. The earliest of the USB standards found in modern hard drives — and exclusively external (see "Performance"). Provides connection to a traditional full-size USB port, provides data transfer rates up to 480 Mbps, as well as a rather low power supply, which is why drives with this type of connection often require additional power. In light of all this, and the advent of the more advanced USB 3.2 standard (see below), USB 2.0 is considered obsolete today and is extremely rare, mainly in inexpensive and early models of drives. However, a drive with this interface can also be connected to a newer USB port — the main thing is that the connectors match.
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USB 3.2 gen1(previously USB 3.1 gen1 and USB 3.0). The standard for connecting external HDDs, which replaced the
...USB 2.0 described above. Uses a traditional full-size USB connector, delivers data transfer speeds up to 4.8 Gbps (600 Mbps) and higher power ratings, making these drives easier to handle without external power. 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 (formerly 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 (supporting 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.
— USB-C 3.2 gen1(formerly USB-C 3.1 gen1 and USB-C 3.0). USB Type-C connection compliant with USB 3.2 gen1 capabilities. These features 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: this is a relatively small (slightly larger than microUSB) socket, which also has a double-sided design. Due to its compact size, USB-C is found both in full-sized PCs and laptops, and in compact gadgets like smartphones and tablets; some drives with this connection are initially capable of "mobile" use.
— USB-C 3.2 gen2(formerly USB-C 3.1 gen2 and USB-C 3.1). Updating and improving the USB-C 3.2 gen1 described above — the same USB-C connector and increased data transfer rate to 10 Gbps (as in the "regular" USB 3.2 gen2).
— IEEE 1394. Also commonly known as "FireWire". A universal connector, similar in capabilities to USB 2.0 (see above), but used much less often, and nowadays is practically obsolete.
— 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 speed, but also in connector: Thunderbolt v2(up to 20 Gbps) uses a miniDisplayPort plug, and Thunderbolt v3(up to 40 Gbps) — USB type C plug (see above). Thus, in some hard drives, USB-C and Thunderbolt connections are implemented through a single hardware connector, which automatically detects which computer input the device is connected to.
— S.A.S. Modification of the SCSI interface, provides data transfer rates up to 6 Gbps (750 Mb / s). It is used mainly in servers, in desktop PCs and laptops it is practically not used.
— Fibre Channel. Professional high-speed interface primarily used in server drives ("Purpose"); similar in many ways to SAS. Allows "hot" replacement of drives; the actual data transfer rate over Fibre Channel, depending on the version, can reach 12.8 Gbps.RPM
For drives used in a PC (see "Intended use"),
5400 rpm(normal) and
7200 rpm(high) are considered standard speeds. There are also
more specific options, including models with the ability to adjust the speed depending on the load. In server HDDs, in turn, higher speeds can be used —
10,000 rpm and even
15,000 rpm.
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.
Operation power consumption
The amount of power consumed by the disk when reading and writing information. In fact, this is the peak power consumption, it is in these modes that the drive consumes the most energy.
HDD power consumption data is needed primarily to calculate the overall system power consumption and power supply requirements for the system. In addition, for laptops that are planned to be used often "in isolation from outlets", it is advisable to choose more economical drives.
Standby power consumption
The amount of power consumed by the disk "idle". In the on state, the disk platters rotate regardless of whether information is being written or read or not — maintaining this rotation takes the energy consumed while waiting.
The lower the power consumption while waiting, the more economical the disk is, the less energy it consumes. At the same time, we note that in fact this parameter is relevant mainly when choosing a drive for a laptop, when energy efficiency is crucial. For stationary PCs, “idle” power consumption does not play a special role, and when calculating the requirements for a power supply, it is necessary to take into account not this indicator, but the power consumption during operation (see above).
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.
