In modern computer systems SATA and SAS interfaces are used to connect main hard drives. As a rule, the first option suits home workstations, the second - server ones, so the technologies do not compete with each other, meeting different requirements. The significant difference in cost and storage space leaves users wondering how SAS differs from SATA and looking for trade-offs. Let's see if it makes sense.
SAS(Serial Attached SCSI) is a serial storage device interface designed around parallel SCSI to execute the same instruction set. Used primarily in server systems.
SATA(Serial ATA) is a serial data exchange interface based on parallel PATA (IDE). It is used in home, office, multimedia PCs and laptops.
If we talk about HDD, then, despite the different specifications and connectors, there are no fundamental differences between the devices. Backward one-sided compatibility makes it possible to connect disks to the server board both one by one and via the second interface.
It is worth noting that both connection options are real for SSDs, but the significant difference between SAS and SATA in this case will be in the cost of the drive: the first can be ten times more expensive with a comparable volume. Therefore, today such a decision, if not uncommon, then it is sufficiently balanced, and is intended for fast corporate-level data centers.
Comparison
As we already know, SAS is used in servers, SATA in home systems. In practice, this means that many users simultaneously access the former and solve many problems, while the latter is dealt with by one person. Accordingly, the server load is much higher, so the disks must be sufficiently fault-tolerant and fast. The SCSI protocols (SSP, SMP, STP) implemented in SAS allow more I / O to be processed concurrently.
Directly for HDD speed The circulation is determined primarily by the spindle speed. For desktop systems and laptops, 5400 - 7200 RPM is necessary and sufficient. Accordingly, it is almost impossible to find a SATA drive with 10,000 RPM (unless you look at the WD VelociRaptor series, designed, again, for workstations), and everything above is absolutely unattainable. SAS HDD spins at least 7200 RPM, 10000 RPM can be considered a standard, and 15000 RPM is a sufficient maximum.
Serial SCSI drives are considered to be more reliable and have higher MTBF. In practice, more stability is achieved through the checksum function. SATA drives, on the other hand, suffer from "silent errors" when data is partially written or damaged, which leads to the appearance of bad sectors.
The main advantage of SAS - two duplex ports, allowing one device to be connected via two channels - also works for the fault tolerance of the system. In this case, the exchange of information will be carried out simultaneously in both directions, and reliability is ensured by the Multipath I / O technology (two controllers insure each other and share the load). The queue of marked commands is built up to 256 deep. Most SATA drives have one half-duplex port, and the NCQ queue depth is no more than 32.
The SAS interface assumes the use of cables up to 10 m long. Up to 255 devices can be connected to one port through expanders. SATA is limited to 1m (2m for eSATA), and only supports one point-to-point connection.
Prospects for further development - what the difference between SAS and SATA is also felt quite sharply. The SAS interface reaches 12 Gbps throughput, and manufacturers are announcing support for 24 Gbps data rates. The latest revision of SATA stopped at 6 Gb / s and will not evolve in this regard.
SATA drives have a very attractive price tag in terms of the cost of 1 GB. In systems where the speed of data access is not critical, and the amount of stored information is large, it is advisable to use them.
table
| SAS | SATA |
| For server systems | Mainly for desktop and mobile systems |
| Uses the SCSI command set | Uses the ATA command set |
| Minimum spindle speed of HDD 7200 RPM, maximum - 15000 RPM | Minimum 5400 RPM, maximum 7200 RPM |
| Supports checksum verification technology when writing data | Large percentage of errors and bad sectors |
| Two duplex ports | One half duplex port |
| Multipath I / O Supported | Point-to-point connection |
| Command queue up to 256 | Command queue up to 32 |
| Cables up to 10 m can be used | Cable length no more than 1 m |
| Bus bandwidth up to 12 Gb / s (in the future - 24 Gb / s) | 6 Gb / s throughput (SATA III) |
| The cost of drives is higher, sometimes significantly | Cheaper in terms of price per GB |
Over the past two years, few changes have accumulated:
- Supermicro is ditching the proprietary "flipped" UIO form factor for controllers. Details will be below.
- LSI 2108 (SAS2 RAID with 512MB cache) and LSI 2008 (SAS2 HBA with optional RAID support) are still in service. The products on these chips, both from LSI and from OEM partners, are fairly well debugged and still relevant.
- LSI 2208 appeared (the same SAS2 RAID with LSI MegaRAID stack, only with a dual-core processor and 1024MB cache) and (an improved version of LSI 2008 with a faster processor and PCI-E 3.0 support).
Moving from UIO to WIO
As you remember, UIO cards are ordinary PCI-E x8 cards, in which the entire element base is located on the back side, i.e. when installed in the left riser is on top. It took such a form factor to install the cards in the lowest slot of the server, which allowed four cards to be placed in the left riser. UIO is not only a form factor for expansion cards, it is also cases designed for installing risers, the risers themselves and motherboards of a special form factor, with a cutout for the lower expansion slot and slots for installing risers.This solution had two problems. First, the non-standard form factor of the expansion cards limited the choice of the client. under the UIO form factor, there are only a few SAS, InfiniBand and Ehternet controllers. Secondly, there is an insufficient number of PCI-E lanes in slots for risers - only 36, of which only 24 lanes for the left riser, which is clearly not enough for four motherboards with PCI-E x8.
What is WIO? At first, it turned out that it was possible to place four boards in the left riser without having to "turn the sandwich butter up", and risers for regular boards appeared (RSC-R2UU-A4E8 +). Then the problem of the lack of lines (now there are 80) was solved by using slots with a higher density of contacts.
| UIO riser RSC-R2UU-UA3E8 + |
 |
| WIO riser RSC-R2UW-4E8 |
Results:
- WIO risers cannot be installed on UIO motherboards (such as X8DTU-F).
- UIO risers cannot be installed in new cards that are WIO-compliant.
- There are risers for WIO (on motherboard) that have a UIO slot for cards. In case you still have UIO controllers. They are used in platforms for Socket B2 (6027B-URF, 1027B-URF, 6017B-URF).
- There will be no new controllers in the UIO form factor. For example, the USAS2LP-H8iR controller on the LSI 2108 chip will be the last one, there will be no LSI 2208 under UIO - just a regular MD2 with PCI-E x8.
PCI-E controllers
V this moment three types are actual: RAID controllers based on LSI 2108/2208 and HBA based on LSI 2308. There is also a mysterious SAS2 HBA AOC-SAS2LP-MV8 on the Marvel 9480 chip, but write about it because of its exoticism. Most use cases for internal SAS HBAs are ZFS storage under FreeBSD and various Solaris flavors. Due to the absence of support problems in these operating systems, the choice falls on LSI 2008/2308 in 100% of cases.LSI 2108
In addition to the UIO "shny AOC-USAS2LP-H8iR, which is mentioned in the addition, two more controllers have been added:
LSI 2108, SAS2 RAID 0/1/5/6/10/50/60, 512MB cache, 8 internal ports (2 SFF-8087 connectors). It is an analogue of the LSI 9260-8i controller, but manufactured by Supermicro, there are minor differences in the board layout, the price is $ 40-50 lower than LSI. All additional LSI options are supported: activation, FastPath and CacheCade 2.0, battery protection of the cache - LSIiBBU07 and LSIiBBU08 (now BBU08 is preferred, it has an expanded temperature range and includes a cable for remote mounting).
Despite the introduction of more efficient controllers based on the LSI 2208, the LSI 2108 is still relevant due to the price reduction. Performance with conventional HDDs is enough in any scenario, the IOPS limit for working with SSDs is 150,000, which is more than enough for most budget solutions.
LSI 2108, SAS2 RAID 0/1/5/6/10/50/60, 512MB cache, 4 internal + 4 external ports. Analogous to the LSI 9280-4i4e controller. Convenient for use in expander bodies, because there is no need to bring the output from the expander outside to connect additional JBODs, or in 1U enclosures for 4 disks, if necessary, to provide the ability to expand the number of disks.Supports the same BBU and activation keys.
LSI 2208
LSI 2208, SAS2 RAID 0/1/5/6/10/50/60, 1024MB cache, 8 internal ports (2 SFF-8087 connectors). It is analogous to the LSI 9271-8i controller. The LSI 2208 is a further development of the LSI 2108. The processor has become a dual-core, which allowed us to raise the IOPS performance limit as much as 465000. Added support for PCI-E 3.0 and increased to 1GB cache.
The controller supports BBU09 cache battery protection and CacheVault flash protection. Supermicro supplies them under the part numbers BTR-0022L-LSI00279 and BTR-0024L-LSI00297, but it is easier to purchase from us through the LSI sales channel (the second part of the part numbers are the native LSI part numbers). MegaRAID Advanced Software Options activation keys are also supported, part numbers: AOC-SAS2-FSPT-ESW (FastPath) and AOCCHCD-PRO2-KEY (CacheCade Pro 2.0).
LSI 2308 (HBA)
LSI 2308, SAS2 HBA (with IR firmware - RAID 0/1 / 1E), 8 internal ports (2 SFF-8087 connectors). This is the same controller, comes with different firmwares. AOC-S2308L-L8e - IT firmware (pure HBA), AOC-S2308L-L8i - IR firmware (with RAID 0/1 / 1E support). The difference is that L8i can work with IR and IT firmware, L8e - only with IT, IR firmware is blocked. Analogous to the LSI 9207-8 controller i... Differences from LSI 2008: faster chip (800 MHz, as a result - IOPS limit increased to 650 thousand), PCI-E 3.0 support appeared. Application: software RAID "s (ZFS, for example), budget servers.
On the basis of this chip, there will be no cheap controllers with support for RAID-5 (iMR stack, from ready-made controllers - LSI 9240).
Onboard controllers
In the latest products (X9 boards and platforms with them), Supermicro denotes the presence of a SAS2 controller from LSI with the number "7" in the part number, and the number "3" for the chipset SAS (Intel C600). However, no distinction is made between LSI 2208 and 2308, so be careful when choosing a board.- The LSI 2208-based controller soldered on the motherboards has a maximum of 16 disks. When adding 17, it simply will not be detected, and in the MSM log you will see the message "PD is not supported". Compensation for this is significantly more low price... For example, a bundle "X9DRHi-F + external controller LSI 9271-8i" will cost about $ 500 more than X9DRH-7F with LSI 2008 on board. It is not possible to bypass this limitation by flashing it into the LSI 9271 - flashing another SBR block, as in the case of the LSI 2108, does not help.
- Another feature is the lack of support for CacheVault modules, the boards simply lack space for a special connector, so only BBU09 is supported. The possibility of installing the BBU09 depends on the enclosure used. For example, LSI 2208 is used in 7127R-S6 blade servers, there is a BBU connector there, but to mount the module itself, you need an additional MCP-640-00068-0N Battery Holder Bracket.
- SAS HBA (LSI 2308) firmware will be needed now, because in DOS on any of the boards with LSI 2308 sas2flash.exe does not start with the error "Failed to initialize PAL".
Controllers in Twin and FatTwin platforms
Some 2U Twin 2 platforms are available in three versions, with three kinds of controllers. For instance:- 2027TR-HTRF + - Chipset SATA
- 2027TR-H70RF + - LSI 2008
- 2027TR-H71RF + - LSI 2108
- 2027TR-H72RF + - LSI 2208
| BPN-ADP-SAS2-H6IR (LSI 2108) |
 |
| BPN-ADP-S2208L-H6iR (LSI 2208) |
| BPN-ADP-SAS2-L6i (LSI 2008) |
Supermicro xxxBE16 / xxxBE26 cases
Another topic that is directly related to controllers is the modernization of cases with. There are varieties with an additional cage for two 2.5 "drives located on the rear panel of the case. Purpose - a dedicated disk (or mirror) for system boot. Of course, the system can be loaded by allocating a small volume from another disk group or from additional disks fixed inside the case (in 846 cases, you can install additional fasteners for one 3.5 "or two 2.5" drives), but the updated modifications are much more convenient:
Moreover, these additional disks do not have to be connected to the chipset SATA controller... Using the SFF8087-> 4xSATA cable, you can connect to the main SAS controller through the SAS expander output.
P.S. Hope the information was helpful. Don't forget that the most full information and technical support for Supermicro, LSI, Adaptec by PMC and other vendors, contact True System.
For over 20 years, the parallel bus interface has been the most common communication protocol for most digital storage systems. But with the growing demand for bandwidth and flexibility, the shortcomings of two of the most common parallel interface technologies, SCSI and ATA, have become apparent. Lack of compatibility between parallel SCSI and ATA interfaces - different connectors, cables and used command sets - increases the cost of maintaining systems, scientific research and development, training and qualification of new products.
Today, parallel technologies still satisfy users of modern enterprise systems in terms of performance, but the growing demands for higher speeds, better data security during transmission, reduced physical size, as well as wider standardization are calling into question the ability of a parallel interface without unnecessary to keep pace with rapidly growing CPU performance and storage speeds on hard drives... In addition, in conditions of austerity, it is becoming increasingly difficult for enterprises to find funds for the development and maintenance of various types of connectors. rear panels server enclosures and external disk arrays, heterogeneous interface compatibility testing, and heterogeneous connection inventory for I / O.
The use of parallel interfaces also presents a number of other problems. Parallel data transmission over wide stub cables is prone to crosstalk, which can create additional interference and lead to signal errors — avoiding this trap requires slowing down the signal rate or limiting the cable length, or both. Termination of parallel signals is also associated with certain difficulties - you have to terminate each line separately, usually this operation is performed by the last accumulator in order to prevent signal reflection at the end of the cable. Finally, the large cables and connectors used in parallel interfaces make these technologies unsuitable for new compact computing systems.
Introducing SAS and SATA
Serial technologies such as Serial ATA (SATA) and Serial Attached SCSI (SAS) overcome the architectural limitations inherent in traditional parallel interfaces. These new technologies got their name from the method of signal transmission, when all information is transmitted sequentially (English serial), in a single stream, as opposed to multiple streams, which are used in parallel technologies. The main advantage of the serial interface is that when data is transferred in a single stream, it moves much faster than using the parallel interface.Serial technologies combine many bits of data into packets and then transmit them over cable at speeds up to 30 times faster than parallel interfaces.
SATA extends the capabilities of traditional ATA technology by allowing data transfer between disk drives at speeds of 1.5 GB per second and above. With its low cost per gigabyte, SATA will remain the dominant disk interface in desktops, entry-level servers and networked storage systems where cost is a major consideration.
SAS, the successor to parallel SCSI, builds on the proven functionality of its predecessor and promises to greatly expand the capabilities of today's enterprise storage systems. SAS has many benefits that traditional storage solutions do not offer. In particular, SAS allows up to 16,256 devices to be connected to a single port and provides reliable point-to-point serial connections at speeds up to 3 Gb / s.
In addition, with a smaller SAS connector, it provides full dual-port connectivity for both 3.5 "and 2.5" drives (previously only available with 3.5 "Fiber Channel drives). This is very useful function when you need to place a large number of redundant drives in a compact system, such as a low-profile blade server.
SAS improves the addressing and connectivity of drives with hardware extenders that allow you to connect a large number of drives to one or more host controllers. Each expander provides connections for up to 128 physical devices which can be other host controllers, other SAS expanders or disk drives. This design scales well and allows you to create enterprise-scale topologies that easily support multisite clustering for automatic recovery systems in the event of a failure and to evenly distribute the load.
One of the major benefits of the new serial technology is that the SAS interface will also be compatible with lower-cost SATA drives, allowing system designers to use both types of drives in the same system without spending additional money to support two different interfaces. Thus, SAS, the next generation of SCSI technology, overcomes the existing limitations of parallel technologies in terms of performance, scalability and data availability.
Multiple levels of compatibility
Physical compatibilityThe SAS connector is universal and SATA compatible in form factor. This allows both SAS and SATA drives to be directly connected to the SAS system and thus use the system for either mission-critical applications that require high performance and fast data access, or for more cost-effective applications with a lower cost per gigabyte.
The SATA command set is a subset of the SAS command set, which provides compatibility between SATA devices and SAS controllers. However, SAS drives cannot work with a SATA controller, so they are equipped with special keys on the connectors to eliminate the possibility of incorrect connection.
In addition, the physical characteristics of the SAS and SATA interfaces are similar, allowing the new universal SAS backplane to accommodate both SAS and SATA drives. As a result, there is no need to use two different rear panels for SCSI and ATA drives. This design compatibility benefits both backplane manufacturers and end users, because this reduces the cost of equipment and design.
Protocol Compatibility
SAS technology includes three types of protocols, each of which is used to transfer data different types via the serial interface, depending on which device is being accessed. The first is the Serial SCSI Protocol SSP, which sends SCSI commands, and the second is the SCSI Management Protocol (SMP), which transfers control information to the expanders. The third, SATA Tunneled Protocol STP, establishes a connection that allows the transmission of SATA commands. By using these three protocols, the SAS interface is fully compatible with existing SCSI applications, management software, and SATA devices.
This multi-protocol architecture, combined with the physical compatibility of SAS and SATA connectors, makes SAS technology a versatile glue between SAS and SATA devices.
Benefits of compatibility
SAS and SATA interoperability offers a variety of benefits to system designers, assemblers, and end users.
System designers can use the same rear panels, connectors and cable connections due to SAS and SATA compatibility. Upgrading a system from SATA to SAS is essentially a matter of replacing disk drives. In contrast, for traditional parallel users, the move from ATA to SCSI means replacing back panels, connectors, cables and drives. Other cost-effective benefits of sequential technology interoperability include simplified certification and material management.
VAR resellers and system builders can easily and quickly reconfigure custom systems by simply installing the appropriate disk drive into the system. There is no need to work with incompatible technologies and use special connectors and different cable connections. What's more, the added flexibility to balance price and performance will allow VAR resellers and system builders to better differentiate their products.
For end users, SATA and SAS compatibility means a new level of flexibility when it comes to choosing the right price / performance ratio. SATA drives will become the best solution for inexpensive servers and storage systems, while SAS drives provide maximum performance, reliability, and management software compatibility. The ability to upgrade from SATA drives to SAS drives without the need to purchase a new system greatly simplifies the purchasing decision process, protects your system investment and lowers your total cost of ownership.
Co-development of SAS and SATA protocols
January 20, 2003 SCSI Trade Association (STA) and Working group The Serial ATA (SATA) II Working Group announced a collaboration to ensure system-level compatibility of SAS technology with SATA disk drives.The two organizations are working together, as well as the joint efforts of storage vendors and standards committees, to provide even more precise interoperability guidelines to help system designers, IT professionals, and end users fine-tune their systems to achieve optimal performance. and reliability and lower total cost of ownership.
The SATA 1.0 specification was approved in 2001 and today there are SATA products on the market from different manufacturers... The SAS 1.0 specification was approved in early 2003, and the first products are expected to hit the market in the first half of 2004.
SAS (Serial Attached SCSI)- serial computer interface designed to connect various devices data storage, for example, and tape drives... SAS is designed to replace the parallel SCSI interface and uses the same SCSI command set.
SAS is backward compatible with SATA interface: SATA II and SATA 6 Gb / s devices can be connected to a SAS controller, but SAS devices cannot be connected to a SATA controller. The latest SAS implementation provides data transfer rates up to 12Gbps per line. 24Gb / s SAS specification expected by 2017
SAS combines the advantages of SCSI interfaces (deep sorting of the command queue, good scalability, high noise immunity, large maximum length cables) and Serial ATA (thin, flexible, cheap cables, hot-plug, point-to-point topology that allows you to achieve more performance in complex configurations) with new unique features such as an advanced connection topology using hubs called SAS- expanders (SAS expanders), connecting two SAS channels to one (both to increase reliability and performance), work on one disk with both SAS and SATA interfaces.
In combination with new system addressing, this allows you to connect up to 128 devices per port and have up to 16256 devices on the controller, while no manipulation of jumpers, etc. is required. The limitation of 2 Terabytes on the volume of the logical device has been removed.
The maximum cable length between two SAS devices is 10 m when using passive copper cables.
Actually, the SAS data transfer protocol means three protocols at once - SSP (Serial SCSI Protocol), which provides the transfer of SCSI commands, SMP (SCSI Management Protocol), which works with SCSI control commands and is responsible, for example, for interacting with SAS expanders, and STP (SATA Tunneled Protocol), which implements support for SATA devices.
The currently produced ones have internal SFF-8643 connectors (it can also be called mini SAS HD), but there may still be SFF-8087 (mini SAS) connectors, to which 4 SAS channels are output.
The external version of the interface uses the SFF-8644 connector, but the SFF-8088 connector may still be encountered. It also supports four SAS channels.
SAS controllers are fully compatible with SATA drives and SATA baskets / backplanes- connection is usually carried out using cables:. The cable looks something like this:
SFF-8643 -> 4 x SAS / SATA
Usually SAS baskets / backplanes have SATA connectors on the outside and you can always insert regular SATA drives into them, therefore they (such baskets) are usually called SAS / SATA.
However, there are reversible versions of such a cable for connecting a backplane with internal SFF-8087 connectors to a SAS controller that has regular SATA connectors. Such cables are not interchangeable with each other.
SAS drives cannot be connected to a SATA controller or installed in a SATA cage / backplane.
To connect SAS disks to a controller with SFF-8643 or SFF-8087 internal connectors without using SAS baskets, you must use a SFF-8643-> SFF-8482 or SFF-8087-> SFF-8482 cable, respectively.
The existing versions of the SAS interface (1.0, 2.0, and 3.0) are compatible with each other, that is, a SAS2.0 disk can be connected to a SAS 3.0 controller and vice versa. In addition, the upcoming 24 Gb / s version will also be backward compatible.
SAS connector types
| Image | Codename | Also known as | External/ interior |
Number of contacts | Number of devices |
Server hard drive, features of choice
The hard drive is the most valuable component in any computer. After all, it stores information with which the computer and the user work, in the event that we are talking about personal computer... A person, each time sitting down at a computer, expects to run the loading screen now. operating system, and he will begin to work with his data, which will give out "to the mountain" from the depths of the Winchester. If we are talking about a hard disk, or even about their array as part of a server, then there are tens, hundreds and thousands of such users who expect to gain access to personal or work data. And all their quiet work or rest and entertainment depends on these devices, which constantly store data in themselves. Already from this comparison it is clear that requests to hard drives home and industrial class are presented unequal - in the first case, one user works with him, in the second - thousands. It turns out that the second HDD should be more reliable, faster, more stable than the first one many times over, because many users work with it, hope for it. This article will discuss the types of hard drives used in the corporate sector and their design features to achieve the highest reliability and performance.
SAS and SATA drives - so similar and so different
Until recently, the standards of industrial-grade and consumer-grade hard drives differed significantly, and were incompatible - SCSI and IDE, now the situation has changed - the overwhelming majority of the market are hard drives SATA and SAS (Serial Attached SCSI) standards. The SAS connector is versatile in form factor and SATA compatible. This allows you to directly connect to the SAS system both high-speed, but at the same time small capacity (at the time of this writing - up to 300 GB) SAS drives, as well as slower, but many times more capacious, SATA drives (at the time of this writing, up to 2 TB ). Thus, in one disk subsystem, you can combine vital important applications demanding high performance and fast data access, and more cost-effective applications with a lower cost per gigabyte.
This design compatibility benefits both backplane manufacturers and end users by reducing hardware and design costs.
That is, both SAS devices and SATA can be connected to the SAS connectors, and only SATA devices are connected to the SATA connectors.
SAS and SATA - high speed and large capacity... What to choose?
SAS disks, which replaced SCSI disks, fully inherited their main characteristics of a hard drive: spindle speed (15000 rpm) and volume standards (36,74,147 and 300 GB). However, SAS itself is significantly different from SCSI. Let's briefly consider the main differences and features: The SAS interface uses a point-to-point connection - each device is connected to the controller by a dedicated channel, in contrast to it, SCSI works over a common bus.
SAS supports a large number of devices (> 16384), while the SCSI interface supports 8, 16, or 32 devices on the bus.
SAS interface supports data transfer rates between devices at speeds of 1.5; 3; 6 Gb / s, while the SCSI interface bus speed is not allocated to each device, but is divided between them.
SAS supports the connection of slower SATA devices.
SAS configuration is much easier to mount, install. Such a system is easier to scale. In addition, SAS drives inherited the reliability of SCSI hard drives.
When choosing a disk subsystem - SAS or SATA, you need to be guided by what functions will be performed by the server or workstation. To do this, you need to decide on the following questions:
1. How many concurrent, diverse requests will the disk handle? If large - your definitive choice - SAS disks. Also, if your system will serve a large number of users, choose SAS.
2. How much information will be stored on the disk subsystem of your server or workstation? If more than 1-1.5 TB - you should pay attention to the system based on SATA hard drives.
3. What is the budget for the purchase of a server or workstation? It should be remembered that in addition to SAS disks, you will need a SAS controller, which must also be taken into account.
4. Do you plan, as a result, the growth of data volume, increase in productivity or increase in the fault tolerance of the system? If yes, then you need a SAS-based disk subsystem, it is easier to scale and more reliable.
5. Your server will handle critical data and applications - your choice is SAS drives, designed for heavy operating conditions.
Reliable disk subsystem, it is not only high-quality hard drives from a renowned manufacturer, but also an external disk controller... They will be discussed in one of the following articles. Consider SATA disks, what types of these disks are and which should be used when building server systems.
SATA drives: consumer and industrial sector
SATA drives used everywhere, from consumer electronics and home computers to high-performance workstations and servers, differ in subtypes, there are drives for use in household appliances, with low heat dissipation, power consumption, and, as a result, reduced performance, there are mid-range drives for home computers, and there are drives for high-performance systems. In this article we will look at a class of hard drives for performance systems and servers.
Performance characteristics
|
Server grade HDD |
HDD desktop class |
|
|
Rotational speed |
7,200 rpm (nominal) |
7,200 rpm (nominal) |
|
Cache size |
||
|
Average delay time |
4.20ms (nominal) |
6.35ms (nominal) |
|
Baud rate |
||
|
Reading from drive cache (Serial ATA) |
maximum 3 Gb / s |
maximum 3 Gb / s |
|
physical characteristics |
||
|
Capacity after formatting |
1,000,204 MB |
1,000,204 MB |
|
Capacity |
||
|
Interface |
SATA 3Gb / s |
SATA 3Gb / s |
|
Number of sectors available to the user |
1 953 525 168 |
1 953 525 168 |
|
Dimensions (edit) |
||
|
Height |
25.4 mm |
25.4 mm |
|
Length |
147 mm |
147 mm |
|
Width |
101.6 mm |
101.6 mm |
|
0.69 kg |
0.69 kg |
|
|
Impact resistance |
||
|
Impact resistance in working order |
65G, 2ms |
30G; 2 ms |
|
Shock resistance when inoperative |
250G, 2ms |
250G, 2ms |
|
Temperature |
||
|
In working order |
-0 ° C to 60 ° C |
-0 ° C to 50 ° C |
|
Out of service |
-40 ° C to 70 ° C |
-40 ° C to 70 ° C |
|
Humidity |
||
|
In working order |
relative humidity 5-95% |
|
|
Out of service |
relative humidity 5-95% |
relative humidity 5-95% |
|
Vibration |
||
|
In working order |
||
|
Linear |
20-300 Hz, 0.75 g (0 to peak) |
22-330 Hz, 0.75 g (0 to peak) |
|
Arbitrary |
0.004 g / Hz (10 - 300 Hz) |
0.005 g / Hz (10 - 300 Hz) |
|
Out of service |
||
|
Low frequency |
0.05 g / Hz (10 - 300 Hz) |
0.05 g / Hz (10 - 300 Hz) |
|
High frequency |
20-500Hz, 4.0G (0 to peak) |
The table presents characteristics of hard disks from one of the leading manufacturers, one column contains the data of a server-class SATA hard drive, in the other a regular SATA hard drive.
From the table we see that disks differ not only in performance characteristics, but also in performance characteristics, which directly affect the lifespan and successful operation of the hard drive. It should be noted that outwardly these hard drives differ insignificantly. Consider what technologies and features allow you to do this:
Reinforced shaft (spindle) hard disk, for some manufacturers it is fixed at both ends, which reduces the influence of external vibration and contributes to accurate positioning of the head assembly during read and write operations.
The use of special intelligent technologies that take into account both linear and angular vibration, which reduces the time for head positioning and increases the performance of discs by up to 60%
The function of elimination of errors on the operating time in RAID arrays - prevents the loss of hard drives from the RAID, which is a characteristic feature of conventional hard drives.
Adjustment of the flight height of the heads in conjunction with the technology of preventing contact with the surface of the plates, which leads to a significant increase in the life of the disk.
A wide range of self-diagnostic functions that allow you to predict in advance the moment when a hard drive will fail, and to warn the user about this, which allows you to have time to save information to a backup drive.
Features that reduce the rate of unrecoverable read errors, which increases the reliability of the server hard drive compared to conventional hard drives.
Speaking about the practical side of the issue, we can confidently say that specialized hard drives in servers "behave" much better. The technical service receives several times fewer calls for unstable RAID arrays and hard disk failures. The manufacturer's support for the server segment of hard drives is much faster than conventional hard drives, due to the fact that the industrial sector is the priority area of work of any manufacturer of data storage systems. After all, it is in it that the most advanced technologies are used, guarding your information.
Analogue of SAS disks:
Hard drives from the company Western digital VelociRaptor. These 10K RPM drives feature 6Gb / s SATA and 64MB cache. The MTBF of these drives is 1.4 million hours.
More details on the manufacturer's website www.wd.com
You can order a server assembly based on SAS or an analogue of SAS hard drives in our "Status" company in St. Petersburg, you can also buy or order SAS hard drives in St. Petersburg:
- call + 7-812-385-55-66 in St. Petersburg
- write to the address
- leave a request on our website on the "Online Application" page