Drive Cases & Docks: specifications, types

General type of drive pocket. The main division of such devices nowadays is external and internal, however, there are also more specific varieties — docking stations and covers. Here is a more detailed description of each option:

— External. Models used outside of PC / laptop cases and designed to turn internal drives into external ones. Pockets of this type perform two main functions. Firstly, they allow you to connect an HDD and SSD with an "internal" interface, such as SATA, to an external connector, most often USB. Secondly, the pocket provides convenience in storage and transportation and additionally protects the contents from dust, moisture and other adverse factors. Such a device can be useful, for example, on a business trip, where you need to carry a lot of work materials: you can remove the entire hard drive from the computer and keep it with you, using it as an external drive. Another example of application is a healthy HDD or SSD left over from an old system and not needed inside a new computer: such a drive with an external pocket can be a good (and definitely cheaper) alternative to a new purely external device.
Note that although most pockets of this type are made portable, there are also stationary models; see "Purpose" for details.

— Internal. Pockets designed to fit inside a PC, laptop or serve...r case. They can perform different functions, depending on the specialization (for more details, see "Purpose"). So, in laptops, pockets are used to install internal drives in a "non-native" seat. In PCs and servers, the specifics of such devices are somewhat different — they are often used to provide the ability to quickly move drives from one case to another. However, there are also solutions that play the role of adapters — in particular, for installing 2.5" drives in 3.5" slots and for connecting M.2 format SSD modules to PCI-E slots for expansion cards. Note that the interface of the drive in the internal models of such models most often corresponds to the connection interface (see below) — in other words, the same interface is used to connect the drive to the pocket and to connect the pocket with the drive installed to the computer. But, again, there may be exceptions — like the mentioned M.2-PCIe adapters.

— Dock station. A special kind of pockets for external purposes, designed mainly for stationary use. The main difference between “docks” and ordinary external pockets is that in this case, instead of full-fledged drive bays, only sockets for connection are provided — in the form of recesses with connectors. Thus, the drives are installed on the docking station as if on a stand, and with this installation they remain almost completely open. The main advantage of this design is the maximum simplicity and speed of replacement; so it makes sense to use docks in cases where you often have to change the installed HDD / SSD. One example of such an application is professional diagnostics of internal drives: instead of putting the next “patient” right into the case or into a traditional external pocket, it’s easier to use the dock. Also note that there are often several slots for drives in docking stations at once, and individual slots can be reconfigured for different form factors (for more details, see "Drive Slots").

— Case. Usual covers for carrying drives; do not perform any other function than storing the contents and protecting them from dust, moisture and other adverse factors. Usually, covers resist dirt well, but impact resistance can be different, and most often it is low — if this point is important to you, it's ok to clarify it separately.

The general purpose of the pocket.

Note that for different types of such accessories (see above), a different division is used according to purpose. So, external pockets are divided into portable and stationary, and internal pockets are divided into laptop models, PC chassis and server solutions. For docking stations and cases, this parameter is not specified at all: the former initially assume stationary use, the latter, again, are portable by definition.

Here is a more detailed description of the options relevant for external pockets:

— Portable. Models designed for frequent moving from place to place and even for use on the go (for example, connecting to a laptop on the road). Most modern external pockets fall into this category — after all, initially external drives (which such pockets are an alternative to) are also made predominantly portable. The specific features of these accessories may vary, but they are all quite compact and designed for only one internal drive, and they receive energy from the same USB port they are connected to (see "Power").

— Stationary. External pockets designed to stay in one place all the time and do not involve frequent movement and use on the road. Such models are much less common than portable ones; most of them are rather l...arge designs, designed to install 2 or more drives, and are often a kind of "NAS-server without networking". However, there are also models for 1 slot — they usually differ from portable counterparts in the presence of a stand that allows you to put the pocket vertically (so that it takes up less space on the table), and is powered by a power supply unit.

In turn, internal pockets for different purposes have the following specifics:

— For laptops. This type is usually designed to install 2.5" or M.2 form factor drives in the optical drive bay (CD / DVD) — due to the compact size of laptops, this is often the only possible way to install an additional drive.

— Chassis. Pockets designed for regular desktop PCs. Note that the term "chassis" traditionally refers to only one special kind of such pockets — the so-called Mobile Rack, colloquially known as "sled". The main function of such accessories is to provide the ability to quickly move drives from one case to another. To do this, the design provides for two parts: a base, which is mounted in a 5.25" slot on the case, and a removable cartridge, into which the drive is installed directly. To prevent theft or unauthorized physical access, the "sled" can be equipped with a lock that blocks the removal of the drive. Our time is used quite rarely, mainly when working with disk arrays, as well as in some other specific cases — for example, so that after the end of the working day you can take a disk with materials with you or hide it in a safe to ensure confidentiality.
Another kind of PC pockets are adapters for installing drives in non-standard seats. The classic case is the use of a 2.5" laptop drive in a 3.5" desktop case, but nowadays there is a more specific option — the use of an SSD M.2 drive as a PCI-E expansion card (for more details, see "Form factor") .

— For the server. Server systems most often have to deal with large volumes of information that require high reliability and/or speed of access. Thus, most pockets of this purpose are designed for several drives (from two to six) — this allows you to provide the necessary volumes and, if necessary, organize a RAID array of one or another level. At the same time, built-in support for RAID (see below) is not found in such devices — it is easier and more reasonable to organize it using the server itself. It is also worth noting that according to the method of installing disks, such pockets usually refer to “sleds” (see “Chassis” above) — this provides additional convenience, allowing, for example, quickly replacing a failed drive in a RAID array. Server pockets can use specialized connection interfaces like SAS, although traditional SATA is still more popular.

The form factor of the drive that the pocket is designed to hold.

Such accessories are made for standard form factors of internal drives: 3.5 ", 2.5"(often — for both at once), as well as M.2 SSD. Here are the features of each of these options:

— HDD 3.5 ". 3.5" is the traditional form factor of internal drives for full-size desktop PCs. Accordingly, internal pockets for this form factor are used exclusively in PCs or servers, they are too bulky for laptops; moreover, most of these pockets are a chassis — "sled" (see "Purpose"). External solutions turn out to be more bulky than models under 2.5", however, due to the absence of strict restrictions on the size, capacious drives for such pockets are much cheaper than miniature analogues of the same capacity. Also note that most 3.5-inch drives are just traditional hard drives (or hybrid SSHD devices), SSD modules in this form factor are practically not produced.

SSD or HDD 2.5". Therefore, the internal pockets of this form factor are intended primarily for laptops; a classic version of such an accessory is an adapter for installing a drive in an optical drive slot. In PC models, this option has not received much distribution — modern desktops usually have not only 3.5-inch, but also 2.5-inch drive bays; and for a number of reasons, it is more convenient to use 3.5" solutions as quick-release "...sleds" (see above). But for servers, internal pockets of this form factor are available — for several slots; they usually also represent a "sled" chassis. What As for external models, 2.5" pockets are noticeably smaller than 3.5" counterparts, however, drives for them are more expensive per gigabyte of capacity (especially with large volumes).

— SSD or HDD 2.5"/3.5". Models designed for two form factors at once. The meaning of this marking depends on the particular type of pocket. So, in external models and docking stations (see "Type"), it usually means the ability to install a drive of any of the two form factors in your pocket, to choose from. Usually, bays or slots in such models are initially designed for 3.5", and special plugs are used to fix 2.5" drives in such slots (note that there may be fewer such plugs in docks than sockets). A similar design is used in internal models for servers, as well as in PC chassis that look like a "sled" (see "Intended use"). However, in PC models there is another option — adapters for accommodating 2.5" HDD / SSD in 3.5" form factor slots ; such accessories are also included in this category.

— SSD M.2. Form factor designed specifically for miniature internal components, including solid state drives. Dimensions of M.2 peripherals are from 12 to 30 mm wide and from 16 to 110 mm in length, such components are connected through the connector of the same name. External pockets of this form factor are compact in size. In turn, internal models are most often laptop solutions for installing an SSD in an optical drive slot. However, there is also a rather specific option — PC accessories that allow you to connect M.2 drives to a PCI-E slot (like a separate sound card or another expansion card).
Note that the connection via M.2 can be carried out both on the basis of PCI-E and on the basis of SATA; for more details, see "Drive interface", here we note that the current moment and compatibility with a specific drive should be specified separately.

Drive interface provided in the design of the pocket, in other words, a way to connect the drive.

It makes sense to use pockets for internal drives, so the appropriate interfaces are used for connection. Also note that in internal models (see "Type") the interface of the drive is often not specified, since it corresponds to the interface for connecting the pocket itself to the computer. As for specific options, here are the most relevant for today:

— SATA 3. The newest and most advanced, and in storage pockets, the most common version of the SATA interface. This interface is designed for internal storage, primarily hard drives; for SSD, it is relatively poorly suited, since it does not allow realizing all the potential of solid-state memory. Specifically, SATA 3 provides data transfer rates up to 600 MB / s, while earlier SATA drives can also be connected to such connectors — unless the connection speed is limited by the capabilities of a slower interface.
It is worth saying that in addition to traditional 2.5" and 3.5" SATA drives (see "Form factor") connected via the connector of the same name, nowadays you can also find M.2 form factor SSD modules that also use a SATA format connection . Such models are noticeably inferior in speed to solutions for M.2 PCI-E, but they are also cheaper. They are connected to the M.2 socket, which must support SATA.

— SATA 2. The predecessor of the SATA 3 described above; this version allows you to t...ransfer data at speeds up to 300 Mbps. In pockets, it is much less common, mainly among outdated models — for example, external solutions using USB 2.0 (see "Connection").

— PCI-E. A variant found exclusively on M.2 drive models (see Drive Form Factor). Such modules use the M.2 connector, the connection through which is most often implemented in the PCI-E format. At the same time, the specifications, usually, specify the version and number of PCI-E lines — the supported speeds directly depend on this. For example, the marking "PCI-E 3.0 2x" means 2 lines of PCI-E version 3.0; this version provides 984 Mbps per lane, so the overall speed is about 1.97 GB/s. However, nowadays, more advanced options are more common — for example, PCI-E 3.0 4x, where the speed is already about 3.9 Gbps. At the same time, drives and pockets with different versions and the number of PCI-E lanes in this case are usually compatible with each other, except that the speed will be limited by the capabilities of a slower interface.

— SATA/SAS. Models that support connection via two interfaces — SATA or SAS. The latter is a specialized standard used primarily in server systems; pockets with this feature also have a corresponding purpose. And this versatility is achieved due to the fact that SAS controllers are also compatible with SATA drives, so you can provide both types of connectors in your pocket. At the same time, SAS noticeably outperforms SATA in terms of operating speed — it is up to 22.5 Gbps, depending on the version (against a maximum of 6 Gbps in SATA). However, note that the SAS interface does not have a strictly defined type of connector — several types of plugs can be used for such a connection; this point needs to be specified separately.

Model of the chipset installed “under the hood” of the data storage pocket.

In fact, the chipset is a set of chips that ensures the joint functioning of the drive with the rest of the computer components. In the context of pockets, the chipset is responsible for processing data, transmitting it, monitoring temperature and power consumption to optimize performance, etc.

The method of connecting a pocket with an installed drive to a computer, provided for in the design.

Note that this parameter is specified only in cases where the connection interface differs from the drive interface (see above). A similar feature is typical for all external models and docking stations (see "Type"): nowadays they most often use USB 3.2 gen1, less often — USB 2.0 or USB-C of one version or another (see below). In internal solutions, the drive connector rarely differs from the pocket connector, although there are exceptions.

It is also worth mentioning that in external models, the connection method is usually determined by the type of bundled cable; moreover, such a cable is often made removable, with the possibility of replacing it with a “cord” with a different type of plug.

As for specific connection methods, here are their main features:

— USB 2.0. USB is used to connect external peripherals, including pockets; this is the most popular modern interface of this purpose. And version 2.0 is the oldest USB standard in use today. The possibilities of such a connection are very limited — in particular, the power supply through the connector is 2.5 W, and the maximum data transfer rate does not exceed 480 Mbps. This is noticeably slower than even SATA 2 (3 Gbps), not to mention SATA 3 (6Gb/s); so in general this stan...dard is considered obsolete, and in pockets with this type of connection, the overall speed is limited just by the capabilities of USB 2.0. However, maintaining this interface is inexpensive; for simple tasks that are not associated with large volumes of information, it often turns out to be quite enough; in addition, USB 2.0 devices are fully compatible with newer USB ports. So nowadays you can still find pockets with this type of connection — these are basically the simplest and most inexpensive models.

— USB 3.2 gen1. Full size USB connector (not USB-C) compliant with version 3.2 gen1. This version (formerly known as USB 3.1 gen1 and USB 3.0) is the direct successor to USB 2.0, delivering up to 10x faster data transfer rates—up to 4.8Gbps—and more power. The mentioned speed is almost one-on-one with the capabilities of the popular SATA 3 internal interface; therefore, pockets with this type of connection are extremely common nowadays.

— USB-C 3.2 gen1. Connecting to a USB-C connector that complies with version 3.2 gen1. In terms of capabilities, this method is identical to the “normal” USB 3.2 gen1 described above, the difference lies only in the type of connector. USB-C is a relatively new standard used in both fixed and portable electronics. This connector is noticeably smaller than the standard USB A (slightly larger than microUSB), while it has a convenient double-sided design. However, specifically in computers and even laptops, USB-C ports are used much less frequently than full-sized USBs, so this option is relatively rare in pockets.

— USB C 3.2 gen2. Connecting to a USB-C connector that complies with version 3.2 gen2. See above for more details on USB-C in general. And USB 3.2 gen2 (formerly known as 3.1 gen2 or simply 3.1) is the successor to 3.2 gen1, with even more advanced features: the maximum connection speed in this standard is 10 Gbps. On the other hand, for SATA drives, such speed is unnecessary, support for this version is quite expensive, and USB-C 3.2 gen2 connection ports are still relatively rare. Therefore, this option has not received distribution in pockets either: it is provided only in individual models for M.2 SSD with PCI-E connection, where the speed of the internal interface is already measured in tens of gigabits per second.

— PCI-E. Connect to a standard PCI-E slot on the motherboard. In other words, such pockets are connected to the computer in the same way as video adapters, sound cards, and other expansion cards. This design is used in select internal models for M.2 SSD drives; using such a pocket, you can connect a similar drive to a desktop PC even if the native M.2 ports on the motherboard are busy, unavailable, not suitable for connection (for example, they use the SATA interface, while the drive is made for PCI-E), or absent altogether.
Note that such pockets are usually compatible with M.2 PCI-E SSD modules without problems, but compatibility with M.2 SATA should be specified separately (although such functionality is also found). It is also worth mentioning that PCI-E slots and devices for them can have a different number of lines, and the general rule here is this: the number of lines in a slot on the motherboard must be no less than that of the connected board. However, in pockets with such a connection, usually less than 4 lines are provided, so they can be connected to PCI-E connectors starting from 4x.

— IDE. Outdated interface for connecting internal drives. It is extremely rare in modern pockets — in separate models designed to install modern or HDD / SSD in outdated computers without SATA and other relevant connectors.

Support for RAID arrays built into the pocket itself.

A RAID array, by definition, consists of multiple drives, so this feature is only available on models with more than one drive. At the same time, we note that in the case of internal installation of drives, it is more convenient to create arrays using the means of the PC itself or the server. So RAID support is found exclusively in external devices and docking stations (see "Type"); in terms of functionality, such solutions often come close to NAS servers, adjusted for the lack of network functions.

Usually, the meaning of an array is not just to combine the volumes of all drives, but also to increase the speed of access to data and/or increase the reliability of their storage. Specific specifics depend on the RAID level: for example, RAID 0 with “scattering” data blocks over individual disks increases access speed, RAID 1 with information mirroring allows you to save all data even if one drive fails, etc. There is also a simple mode combining the volumes of all disks — it is called JBOD and is used along with RAID. Different pocket models may support different RAID levels, this point should be clarified separately.

The main material from which the body of the pocket is made.

— Plastic / rubber. This category includes models that use plastic and/or rubber in the construction of cases. The specific ratio and features of the use of these materials are different: the body can be all-plastic, have rubber lining at the ends to increase impact protection, be completely covered with rubber, etc. And in covers (see "Type"), these materials can also be supplemented with others — such as EVA, neoprene or even cloth. Anyway, plastic / rubber cases are found exclusively in external models, including docking stations. Such pockets are somewhat inferior to metal pockets in terms of strength and reliability, but they are cheaper, and in normal everyday use, the mentioned difference is not critical.

— Steel. Cases made of metal are most often made of steel, but there are other options (for example, aluminium alloys). In the inner pockets, only this option is found — this is due to a number of features of such accessories. As for external models in this design, they are much stronger and more reliable than plastic ones, besides, the metal case creates an additional feeling of solidity. The downside of these advantages is the higher price.

The number of separate slots for drives provided in the design of the pocket, in other words, the number of drives for which this model is designed.

In addition to models for one slot, nowadays you can find more capacious solutions — for two drives, or even more. Such "multiplying" is found in three types of devices. The first is large-format pockets for stationary purposes (see above), operating in the format of separate storages for a large amount of data. Such models may support RAID arrays (see above) and other special features. The second type of devices with more than one slot are separate docking stations (see "Type") with similar functionality. The third type is server models (see "Purpose") with an internal installation; they again allow the organization of arrays, but by means of the server itself.

Note that external devices with one slot can be powered from the USB port, but several drives in this case inevitably require a separate PSU (see "Power").

The maximum storage capacity supported by the pocket. In models with multiple disks/SSDs (see "Drive Slots"), this item indicates the largest total volume supported by the device; by dividing this capacity by the number of slots, you can determine the maximum allowable capacity of each individual drive.

The limitation on the maximum volume is relevant mainly for external models, including docking stations (see "Type"). This is due to the fact that fundamentally different interfaces are used for the drive and for connecting the pocket itself in such models (most often SATA and USB, respectively, see above for details). For the normal interaction of such interfaces, an electronic controller is required; and the larger the volume of the installed drive (s) — the higher the requirements for the performance of such a controller.

Note that, other things being equal, supporting large volumes is more expensive, and capacious drives themselves are not cheap. Therefore, when choosing according to this indicator, it is worth considering real needs, and not chasing the maximum numbers.

The type of power provided in the design of the pocket.

This parameter is relevant only for external models (in internal solutions, power is determined solely by the connection interface). The options could be:

— USB. Powered by the same USB port used for the main connection. The advantage of this option is obvious: it allows you to do without unnecessary wires and use the pocket regardless of the presence of sockets (which is important, for example, when working with a laptop on the road). At the same time, the power of USB power is generally low, and besides, it directly depends on the version of the connector (see "Connection"). So for pockets with several disks, this option is not suitable in principle. In other cases, you should pay attention to compatibility when connecting to a USB connector of an older version than is supported by the pocket. For example, a model with USB 3.2 gen1 can be physically connected to a USB 2.0 port without any problems, but it may not have enough power for normal operation. However, more modern versions (USB 3.2 gen1 and gen2) practically do not have such compatibility problems.

- Power Supply. Powered by a separate PSU, usually plugged into a power outlet. These pockets are bulkier and less mobile than USB-powered models, they can't work without power outlets nearby, and the extra wire is a bit of a hassle. On the other hand, the power supply is capable of delivering mor...e power than USB, and this power is constant and does not depend on the version of the port to which the drive is connected. So many stationary models use just such a power supply; and for external pockets for two or more drives, this is generally the only available option.

The presence of an active cooling system in the design of the pocket.

Active systems are called systems that forcibly provide heat removal; a classic example is a fan (or a cooler, that is, a fan with a heatsink), such devices are also used in storage pockets. Their main advantage is the high efficiency of heat removal. On the other hand, active cooling creates additional noise, increases size and power consumption, and also affects the price of the design — despite the fact that drive pockets usually do not heat up so much, and the mentioned efficiency is rarely required for them. Thus, this feature is found exclusively among stationary models designed for several drives. Such models can have quite powerful control electronics that generate a lot of heat and require additional cooling, and the mentioned disadvantages are not particularly important for them.

The presence of a cover in the delivery set of the pocket.

The cover is supplied only with external portable models (see "Intended use"). The functions of such an accessory are traditional: it protects the device from dust, moisture and other troubles during storage and transportation, and can also be used to store additional items such as a connection cable or an external power supply. At the same time, covers are usually more convenient and functional than impromptu packaging. They can be made of different materials, each option has its own advantages: soft materials allow you to compactly fold the case when it is not needed, hard materials better protect the contents from bumps and shocks.