Hello! In the last article, we examined in detail the device of the hard drive, but I did not specifically say anything about the interfaces – that is, the ways of interaction between the hard drive and the rest of the computer’s devices, or, more specifically, the methods of interaction (connection) of the hard drive and the computer’s motherboard.
Why didn’t he? And because this topic is worthy of no less volume than an entire article. Therefore, today we will analyze in all details the most popular hard disk interfaces at the moment. I’ll make a reservation right away that an article or a post (as it is more convenient for anyone) this time will have impressive dimensions, but unfortunately there is no way to go without it, because if you write it briefly, it will turn out completely incomprehensible.
Computer hard disk interface concept
First, let’s define an interface. In simple terms (namely, I will use it as much as possible, because the blog is designed for ordinary people, such as you and me), the interface is a way of interaction between deviceswith each other and not only devices. For example, many of you have probably heard about the so-called “friendly” interface of any program. What does it mean? This means that the interaction between a person and a program is easier, which does not require much effort on the part of the user, in comparison with a “not friendly” interface. In our case, the interface is just a way of interaction between the hard drive and the computer’s motherboard. It is a set of special lines and a special protocol (a set of data transfer rules). That is, purely physically, it is a loop (cable, wire), on both sides of which there are inputs, and on the hard disk and the motherboard there are special ports (places where the cable is connected). Thus, the concept of interface – includes a connecting cable and ports,
Well, now the most “juice” of today’s article, let’s go!
Types of interaction between hard drives and the computer motherboard (types of interfaces)
So, first in line we will have the most “ancient” (80s) of all, in modern HDDs it is no longer to be found, this is the IDE interface (aka ATA, PATA).
IDE is translated from English as “Integrated Drive Electronics”, which literally means “built-in controller”. It was only later that the IDE began to be called an interface for data transfer, since the controller (located in the device, usually in hard drives and optical drives) and the motherboard had to be connected with something. It (IDE) is also called ATA (Advanced Technology Attachment), it turns out something like “Advanced Technology Attachment”. The fact is that ATA is a parallel data transfer interface , for which soon (literally right after the release of SATA, which will be discussed below) it was renamed PATA (Parallel ATA).
What can I say, although the IDE was very slow (the bandwidth of the data transfer channel was from 100 to 133 megabytes per second in different versions of the IDE – and that is purely theoretically, in practice it is much less), but it allowed simultaneously connecting two devices to the motherboard , while using one loop.
Moreover, in the case of connecting two devices at once, the line bandwidth was divided in half. However, this is far from the only drawback of the IDE. The wire itself, as can be seen from the figure, is wide enough and when connected will take up the lion’s share of the free space in the system unit, which will negatively affect the cooling of the entire system as a whole. In general, IDE is already outdated morally and physically, for this reason, the IDE connector is no longer found on many modern motherboards, although until recently they were still installed (in the amount of 1 piece) on budget motherboards and on some mainboards in the middle price segment.
The next, no less popular than IDE in its time, interface is SATA (Serial ATA) , a characteristic feature of which is the serial data transfer. It is worth noting that at the time of this writing, it is the most widespread for use in a PC.
There are 3 main variants (revisions) of SATA, differing from each other in bandwidth: rev. 1 (SATA I) – 150 Mb / s, rev. 2 (SATA II) – 300 Mb / s, rev. 3 (SATA III) – 600 Mb / s. But this is only in theory. In practice, the speed of writing / reading hard drives usually does not exceed 100-150 Mb / s, and the remaining speed is not yet in demand and only affects the speed of interaction between the controller and the HDD cache (increases the speed of access to the disk).
Among the innovations, we can note – backward compatibility of all SATA versions (a disk with a SATA rev. 2 connector can be connected to a motherboard with a SATA rev. 3 connector, etc.), improved appearance and convenience of connecting / disconnecting the cable, increased in comparison with IDE cable length (1 meter maximum, versus 46 cm on the IDE interface), NCQ function support starting from the first revision. I hasten to please the owners of old devices that do not support SATA – there are adapters from PATA to SATA , this is a real way out of the situation, allowing you to avoid spending money on buying a new motherboard or a new hard drive.
Also, unlike PATA, the SATA interface provides for “hot swapping” of hard drives, which means that when the power supply of the computer’s system unit is turned on, you can connect / disconnect hard drives. However, to implement it, you will need to dig a little in the BIOS settings and enable the AHCI mode.
The next in line – eSATA (External SATA) – was created in 2004, the word “external” means that it is used to connect external hard drives. Supports hot swapping drives. The length of the interface cable has been increased compared to SATA – the maximum length is now as much as two meters. eSATA is not physically compatible with SATA, but has the same bandwidth.
But eSATA is far from the only way to connect external devices to your computer. For example FireWire is a high-speed serial interface for connecting external devices, including HDD.
Supports hot swapping of hard drives. In terms of bandwidth, it is comparable to USB 2.0, and with the advent of USB 3.0 it even loses in speed. However, it still has an advantage – FireWire is able to provide isochronous data transfer, which contributes to its use in digital video, since it allows data to be transferred in real time. FireWire is undoubtedly popular, but not as popular as USB or eSATA, for example. It is rarely used to connect hard drives; in most cases, various multimedia devices are connected using FireWire.
USB (Universal Serial Bus) is perhaps the most common interface used to connect external hard drives, flash drives and solid state drives (SSD). As in the previous case – there is support for “hot swapping”, a rather large maximum length of the connecting cable – up to 5 meters in case of using USB 2.0, and up to 3 meters – if using USB 3.0. Probably you can make a longer cable length, but in this case, the stable operation of the devices will be questionable.
The data transfer rate of USB 2.0 is about 40 Mb / s, which is generally a low figure. Yes, of course, for ordinary daily work with files, a bandwidth of 40 Mb / s is enough for your eyes, but as soon as it comes to working with large files, you will inevitably start looking towards something faster. But it turns out there is a way out, and its name is USB 3.0, the bandwidth of which, compared to its predecessor, has increased 10 times and is about 380 Mb / s, that is, almost like SATA II, even a little more.
There are two types of USB cable pins, type “A” and type “B”, located on opposite ends of the cable. Type “A” – controller (motherboard), type “B” – connected device.
USB 3.0 (Type “A”) is compatible with USB 2.0 (Type “A”). Types “B” are not compatible with each other, as can be seen from the figure.
Thunderbolt (Light Peak). In 2010, Intel demonstrated the first computer with this interface, and a little later, the equally famous Apple company joined Intel in support of Thunderbolt. Thunderbolt is pretty cool (well, otherwise, Apple knows what is worth investing in), is it worth talking about its support of such features as: the notorious “hot swap”, simultaneous connection with several devices at once, really “huge” data transfer speed (20x faster than USB 2.0).
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The maximum cable length is only 3 meters (apparently more is not needed). Nevertheless, despite all the listed advantages, Thunderbolt is not yet “mass” and is used mainly in expensive devices.
Move on. Next in line we have a couple of very similar interfaces – SAS and SCSI. The similarity of them lies in the fact that they are both used mainly in servers where high performance and the shortest possible access time to the hard disk are required. However, there is a downside to the coin – all the advantages of these interfaces are offset by the cost of the devices that support them. Hard drives that support SCSI or SAS are orders of magnitude more expensive.
SCSI (Small Computer System Interface) is a parallel interface for connecting various external devices (not just hard drives).
It was developed and standardized even slightly earlier than the first version of SATA. Recent versions of SCSI have hot-swap support.
SAS (Serial Attached SCSI), which replaced SCSI, had to solve a number of shortcomings of the latter. And I must say – he succeeded. The fact is that due to its “parallelism” SCSI used a common bus, so only one of the devices could work with the controller at a time, SAS was free from this drawback.
In addition, it is backward compatible with SATA, which is undoubtedly a big plus. Unfortunately, the cost of hard drives with SAS interface is close to the cost of SCSI hard drives, but there is no way to get rid of this, you have to pay for the speed.
If you are not tired yet, I suggest considering another interesting way to connect HDD – NAS (Network Attached Storage). Network-attached storage systems (NAS) are very popular nowadays. In fact, this is a separate computer, a kind of mini-server responsible for storing data. It connects to another computer via a network cable and is controlled from another computer through a regular browser. All this is necessary in cases where a large disk space is required, which is used by several people at once (in the family, at work). Data from the NAS is transmitted to users’ computers either via a regular cable (Ethernet) or using Wi-Fi. In my opinion, a very handy thing.
I think that’s all for today. I hope you enjoyed the material, I suggest subscribing to blog updates so as not to miss anything (form in the upper right corner) and we will meet with you in the next blog articles.
This article will focus on what allows you to connect a hard drive to your computer, namely, the hard drive interface. More precisely, about the interfaces of hard drives, because a great variety of technologies for connecting these devices have been invented over the entire period of their existence, and the abundance of standards in this area can confuse an inexperienced user. However, about everything in order.
Purpose
Hard disk interfaces (or, strictly speaking, external storage interfaces, since they can be not only hard disks, but also other types of drives, for example, optical drives) are designed to exchange information between these external memory devices and the motherboard. Hard drive interfaces, as much as the physical parameters of the drives, affect many of the drive’s performance and performance. In particular, the interfaces of the drives determine their parameters such as the speed of data exchange between the hard drive and the motherboard, the number of devices that can be connected to a computer, the ability to create disk arrays, the possibility of hot plugging, support for NCQ and AHCI technologies, etc. … It also depends on the hard disk interface which cable,
SCSI – Small Computer System Interface
SCSI is one of the oldest interfaces designed for connecting storage devices in personal computers. This standard appeared in the early 1980s. One of its developers was Alan Shugart, also known as the inventor of floppy disk drives.
The SCSI standard (traditionally this abbreviation is read in Russian transcription as “fairy tale”) was originally intended for use in personal computers, as evidenced by the very name of the format – Small Computer System Interface, or a system interface for small computers. However, it so happened that drives of this type were used mainly in top-class personal computers, and later in servers. This was due to the fact that, despite the successful architecture and a wide range of commands, the technical implementation of the interface was rather complicated and did not fit the cost for mass PCs.
Nevertheless, this standard had a number of capabilities that are not available for other types of interfaces. For example, a Small Computer System Interface cable can have a maximum length of 12 m and a data transfer rate of 640 MB / s.
Like the later IDE interface, the SCSI interface is parallel. This means that the interface uses buses that carry information over multiple conductors. This feature was one of the limiting factors for the development of the standard, and therefore, as its replacement, a more advanced, serial SAS standard (from Serial Attached SCSI) was developed.
SAS – Serial Attached SCSI
Serial Attached SCSI was developed as an improvement on the rather old Small Computers System Interface for connecting hard drives. Despite the fact that Serial Attached SCSI takes advantage of the main advantages of its predecessor, it nevertheless has many advantages. Among them, the following are worth noting:
- Use of a common bus for all devices.
- The serial communication protocol used by SAS allows fewer signal lines to be used.
- No bus termination required.
- Almost unlimited number of connected devices.
- Higher bandwidth (up to 12 Gbps). Future implementations of the SAS protocol are expected to support data rates up to 24 Gbps.
- The ability to connect to the SAS controller drives with Serial ATA interface.
Typically, Serial Attached SCSI systems are built around several components. The main components include:
- Target devices. This category includes the actual drives or disk arrays.
- Initiators are microcircuits designed to generate requests to target devices.
- Data delivery system – cables connecting target devices and initiators
Serial Attached SCSI connectors come in a variety of shapes and sizes, depending on the type (external or internal) and the SAS versions. Below is the internal SFF-8482 connector and the external SFF-8644 connector designed for SAS-3:
A few examples of the appearance of SAS cords and adapters: HD-Mini SAS cord and SAS-Serial ATA adapter cord.
Firewire – IEEE 1394
Firewire hard drives are quite common today. Although you can connect any type of peripheral device to your computer through the Firewire interface, and it cannot be called a specialized interface designed for connecting exclusively hard drives, nevertheless, Firewire has a number of features that make it extremely convenient for this purpose.
The Firewire interface was developed in the mid-1990s. The beginning of the development was laid by the well-known company Apple, which needed its own, other than USB, bus for connecting peripheral equipment, primarily multimedia. The specification that describes the operation of the Firewire bus is called IEEE 1394.
Firewire is one of the most commonly used high-speed serial external bus formats today. The main features of the standard include:
- Hot-pluggable devices.
- Open bus architecture.
- Flexible topology for connecting devices.
- Data transfer rates varying over a wide range – from 100 to 3200 Mbit / s.
- The ability to transfer data between devices without a computer.
- The possibility of organizing local networks using a bus.
- Bus power transmission.
- A large number of connected devices (up to 63).
To connect hard drives (usually by means of external enclosures for hard drives) via the Firewire bus, as a rule, a special SBP-2 standard is used, using the command set of the Small Computers System Interface protocol. It is possible to connect Firewire devices to a regular USB connector, but this requires a special adapter.
For more details, see the IEEE 1394 – fireWire standard.
IDE – Integrated Drive Electronics
The abbreviation IDE is undoubtedly familiar to most personal computer users. The interface standard for connecting IDE hard drives was developed by a well-known hard drive manufacturer – Western Digital. The advantage of IDE over other interfaces that existed at that time, in particular, the Small Computers System Interface, as well as the ST-506 standard, was that there was no need to install a hard disk controller on the motherboard. The IDE standard implied the installation of a drive controller on the drive case itself, and only the host interface adapter for connecting IDE drives remained on the motherboard.
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This innovation has improved the performance of the IDE drive by reducing the distance between the controller and the drive itself. In addition, the installation of an IDE controller inside the hard drive case made it possible to somewhat simplify both motherboards and the production of the hard drives themselves, since the technology gave freedom to manufacturers in terms of the optimal organization of the drive logic.
The new technology was originally called Integrated Drive Electronics. Subsequently, a standard describing it was developed, called ATA. This name is derived from the last part of the name of the PC / AT family of computers by adding the word Attachment.
A dedicated IDE cable is used to connect a hard drive or other device such as an Integrated Drive Electronics optical drive to the motherboard. Since ATA refers to parallel interfaces (therefore it is also called Parallel ATA or PATA), that is, interfaces that provide for the simultaneous transfer of data over several lines, its data cable has a large number of conductors (usually 40, and in the latest versions of the protocol it was possible to use 80-wire cable). The typical data cable for this standard is flat and wide, but there are also round cables. The power cable for Parallel ATA drives has a 4-pin connector and is connected to the computer’s power supply.
Below are examples of IDE cable and round PATA data cable:
Due to the comparative cheapness of Parallel ATA drives, the simplicity of the interface implementation on the motherboard, as well as the ease of installation and configuration of PATA devices for the user, Integrated Drive Electronics drives for a long time ousted devices of other types of interface from the market of hard drives for budget-level personal computers.
However, the PATA standard also has several disadvantages. First of all, this is a limitation on the length that a Parallel ATA data cable can have – no more than 0.5 m. In addition, the parallel organization of the interface imposes a number of restrictions on the maximum data transfer rate. Does not support the PATA standard and many of the advanced features that other types of interfaces have, such as hot-plugging devices.
SATA – Serial ATA
The SATA (Serial ATA) interface, as the name suggests, is an enhancement to ATA. This improvement consists, first of all, in the conversion of the traditional parallel ATA (Parallel ATA) into a serial interface. However, the differences between the Serial ATA standard and the traditional one are not limited to this. In addition to changing the data transfer type from parallel to serial, the data and power connectors have also changed.
Below is the SATA data cable:
This made it possible to use a significantly longer cable and to increase the data transfer rate. However, the downside was the fact that PATA devices, which were present on the market in huge quantities before the advent of SATA, became impossible to directly plug into the new connectors. True, most new motherboards still have old connectors and support connecting older devices. However, the reverse operation – connecting a new type of drive to an old motherboard usually causes much more problems. For this operation, the user usually needs a Serial ATA to PATA adapter. The power cable adapter is usually relatively simple in design.
Serial ATA to PATA Power Adapter:
More complex, however, is the case with a device such as an adapter for connecting a serial interface device to a parallel interface connector. Usually, an adapter of this type is made in the form of a small microcircuit.
Nowadays the Serial ATA interface has practically supplanted Parallel ATA, and PATA drives can now be found mainly only in fairly old computers. Another feature of the new standard that has ensured its widespread popularity is support for NCQ and AHCI technologies.
You can tell a little more about NCQ technology. The main advantage of NCQ is that it allows you to use ideas that have long been implemented in the SCSI protocol. In particular, NCQ supports a system for sequencing read / write operations to multiple drives installed in the system. Thus, NCQ can significantly improve the performance of storage devices, especially hard disk arrays.
To use NCQ, technology support is required from the hard disk side as well as the motherboard host adapter. Almost all adapters that support AHCI also support NCQ. In addition, NCQ is supported by some older proprietary adapters. Also, for the operation of NCQ, its support from the operating system is required.
eSATA – External SATA
Separately, it is worth mentioning the eSATA (External SATA) format, which seemed promising in its time, but has not received wide distribution. As you might guess from the name, eSATA is a type of Serial ATA designed for connecting exclusively external drives. The eSATA standard offers most of the capabilities of the standard for external devices, i.e. internal Serial ATA, in particular, the same signal and command system and the same high speed.
However, eSATA has some differences from the internal bus standard that spawned it. In particular, eSATA supports longer data cables (up to 2m) and also has higher power requirements for drives. In addition, eSATA connectors are slightly different from standard Serial ATA connectors.
Compared to other external buses such as USB and Firewire, eSATA, however, has one major drawback. While these buses allow the device to be powered through the bus cable itself, the eSATA drive requires dedicated power connectors. Therefore, despite the relatively high data transfer rate, eSATA is currently not very popular as an interface for connecting external drives.
Conclusion
Information stored on a hard disk cannot become useful to the user and available to application programs until it is accessed by the computer’s central processor. Hard drive interfaces are the means for communication between these drives and the motherboard. Today, there are many different types of hard drive interfaces, each of which has its own advantages, disadvantages, and characteristic features. We hope that the information given in this article will be in many ways useful to the reader, because the choice of a modern hard disk is largely determined not only by its internal characteristics, such as capacity, cache memory, access and rotation speed, but also by the interface for which it was designed.
Good day! In the last post, we examined the hard device in detail, but I did not specifically say anything about the interfaces – that is, the ways of interaction between the hard and the rest of the computer’s devices, or, more specifically, the methods of interaction (connection) between the hard and the motherboard of the clerk.
Why didn’t he? And because this topic is worthy of the volume of no less than an entire post. So now let’s take a closer look at the most popular hard disk interfaces today. I’ll make a reservation right away that a post or a post (as it is more convenient for anyone) this time will have impressive dimensions, but unfortunately there is no way to go without it, because if you write it briefly, it will not be entirely clear.
PC hard disk interface concept
First, let’s define an interface. In simple terms (namely, I will use it as much as possible, since the blog is designed for ordinary people, such as you and me), an interface is a way of interacting devices with each other and not only devices. For example, many of you must have heard about the so-called “friendly” interface of any program. What does it mean? This means that the interaction of a person and a program is easier, which does not require a lot of effort on the part of the user, in comparison with the “not friendly” interface. In our case, the interface is just a way of interaction between the hard and the motherboard of the writer. It is a set of special lines and a special protocol (a set of data transfer rules). That is, purely physically – a loop (cable, wire), on 2 sides of which there are inputs, and on the hard disk and the motherboard there are special ports (places where the cable is connected). Thus, the concept of an interface includes a connecting cable and ports located on the devices it connects.
Types of interaction of screws and the motherboard of the computer (types of interfaces)
Well, first in line we will have the most “ancient” (80s) of all, in modern HDDs it is no longer to be found, this is the IDE interface (aka ATA, PATA).
IDE is translated from English as “Integrated Drive Electronics”, which literally means “built-in controller”. It was only later that the IDE began to be called an interface for data transfer, since the controller (located in the device, mainly in hard drives and optical drives) and the motherboard had to be connected with something. It (IDE) is also called ATA (Advanced Technology Attachment), it turns out something like “Advanced Technology Attachment”. The point is that ATA is a parallel data transfer interface, for which soon (literally right after the release of SATA, which will be discussed below) it was renamed PATA (Parallel ATA).
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What can I say, although the IDE was very slow (the bandwidth of the data transfer channel was from 100 to 133 megabytes per second in different versions of the IDE – and that is purely theoretically, in practice it is much less), but it allowed connecting two devices at once to the motherboard , while using one loop.
Moreover, in the case of connecting 2 devices at once, the line bandwidth was divided in half. But, this is far from the only drawback of the IDE. The wire itself, as can be seen from the figure, is wide enough and when connected will take up the lion’s share of free space in the system unit, which will negatively affect the cooling of the entire system as a whole. In general, IDE is already outdated morally and physically, for this reason, the IDE connector is no longer found on many modern motherboards, although until recently they were still installed (in the amount of 1 piece) on budget motherboards and on some mainboards in the middle price segment.
The next, no less popular than IDE in its time, interface is SATA (Serial ATA), a characteristic feature of which is the serial data transfer. It is worth noting that at the time of this writing, it is the most widespread for use in computers.
There are three main variants (revisions) of SATA, differing from each other in bandwidth: rev. 1 (SATA I) – 150 Mb / s, rev. 2 (SATA II) – 300 Mb / s, rev. three (SATA III) – 600 Mb / s. But this is only in theory. In practice, the speed of writing / reading screws generally does not exceed 100-150 MB / s, and the remaining speed is not yet in demand and only affects the speed of interaction between the controller and the HDD cache (increases the speed of access to the disk).
Among the innovations, I note – backward compatibility of all SATA versions (a disk with a SATA rev. 2 connector can be connected to a motherboard with a SATA rev. Three connector, etc.), improved appearance and convenience of connecting / disconnecting the cable, increased compared to IDE cable length (1 meter maximum, versus 46 cm on the IDE interface), support for the NCQ function starting from the first revision. I hasten to please the owners of old devices that do not support SATA – there are adapters from PATA to SATA, this is a real way out of the situation, allowing you to avoid spending money on buying a new motherboard or a new hard drive.
Also, unlike PATA, the SATA interface provides for “hot swapping” of cans, which means that when the computer’s power is on, you can connect / disconnect hard drives. Only for its implementation it will be necessary to dig a little in the BIOS settings and turn on the AHCI mode.
eSATA (External SATA)
The next on the list – eSATA (External SATA) – was created in 2004, the word “external” means that it is used to connect external hard drives. Supports hot swapping drives. The length of the interface cable is increased compared to SATA – the maximum length is currently as much as two meters. eSATA is not physically compatible with SATA, but has the same bandwidth.
But eSATA is far from the only way to connect external devices to your computer. For example FireWire is a high-speed serial interface for connecting external devices, including HDD.
Supports hot swappable screws. In terms of bandwidth, it is comparable to USB 2.0, and with the advent of USB 3.0 it even loses in speed. However, it still has an advantage – FireWire can provide isochronous data transfer, which contributes to its use in digital video, since it makes it possible to transfer data in real time. FireWire is undoubtedly popular, but not as popular as USB or eSATA, for example. It is rarely used to connect screws; in most cases, various multimedia devices are connected using FireWire.
USB (Universal Serial Bus)
USB (Universal Serial Bus) is perhaps the most common interface used to connect external hard drives, flash drives and solid state drives (SSD). As in the previous case, there is support for “hot swapping”, a rather large maximum length of the connecting cable – up to 5 meters in case of using USB 2.0, and up to three meters – if using USB 3.0. Probably you can make a longer cable length, but in this case, the stable operation of the devices will be questionable.
The data transfer rate of USB 2.0 is about 40 Mb / s, which is generally a low figure. Yes, of course, for ordinary daily work with files, a bandwidth of 40 Mb / s is enough for your eyes, but as soon as it comes to working with large files, you will inevitably start looking towards something faster. But it turns out there is a way out, and its name is USB 3.0, the bandwidth of which, compared to its predecessor, has increased 10 times and is about 380 Mb / s, that is, almost like SATA II, even a little more.
There are two types of USB cable pins, type “A” and type “B”, located on opposite ends of the cable. Type “A” – controller (motherboard), type “B” – connected device.
USB 3.0 (Type “A”) is compatible with USB 2.0 (Type “A”). Types “B” are not compatible with each other, as can be seen from the figure.
Thunderbolt (Light Peak)
Thunderbolt (Light Peak). In 2010, Intel demonstrated the first computer with this interface, and a little later, the no less famous Apple company joined Intel in support of Thunderbolt. Thunderbolt is cool enough (well, how else, Apple knows what is worth investing in), is it worth talking about its support of such features as: the notorious “hot swap”, immediate connection with several devices at once, really “huge” data transfer speed (20x faster than USB 2.0).
The maximum cable length is only three meters (apparently more is not needed). Nevertheless, despite all the listed advantages, Thunderbolt is not yet “mass” and is used mainly in expensive devices.
Move on. Next in line we have a pair of very similar interfaces – SAS and SCSI. The similarity of them lies in the fact that they are both used mainly in servers where high performance and the shortest possible access time to the hard disk are required. But, there is also a downside to the coin – all the advantages of these interfaces are offset by the cost of devices that support them. Hard drives that support SCSI or SAS are orders of magnitude more expensive.
SCSI (Small Computer System Interface)
SCSI (Small Computer System Interface) is a parallel interface for connecting various external devices (not just hard drives).
It was developed and standardized even slightly earlier than the first version of SATA. Recent versions of SCSI have hot-swap support.
SAS (Serial Attached SCSI)
SAS (Serial Attached SCSI), which replaced SCSI, had to solve a number of shortcomings of the latter. And I must say – he succeeded. The fact is that due to its “parallelism” SCSI used a common bus, so only one of the devices could work with the controller at once, SAS was free from this drawback.
In addition, it is backward compatible with SATA, which is undoubtedly a big plus. Unfortunately, the price of screws with SAS interface is close to the cost of SCSI hard drives, but there is no way to get rid of this, you have to pay for the speed.
NAS (Network Attached Storage)
If you are not tired yet, I suggest considering another cool way to connect HDD – NAS (Network Attached Storage). Nowadays, network-attached storage systems (NAS) are very popular. In fact, this is a separate computer, a kind of mini-server responsible for storing data. It connects to another PC via a network cable and is controlled from another computer through a regular browser. All this is necessary in cases where a large disk space is required, which is used by several people at once (in the family, at work). Data from the network storage is transmitted to user scribes either over a regular cable (Ethernet) or using Wi-Fi. In my opinion, a very handy thing.
