In-depth understanding of the new standard before it is necessary to review existing technology. For a long time, hard disk technology, are focused on two aspects of transmission speed and capacity. Basically, since the knowledge of computer, we have been in use Ultra ATA. This extension of the long-interface technology, there are better ways become obsolete and need to improve:
We all know that the data cable is too thick, the installation is not convenient, seriously affected the air circulation inside the chassis, the chassis is not conducive to heat, is the traditional IDE interface, Ultra ATA hard drive to the shortcomings of life. However, IDE hard disk, there are many other limitations, probably not many people are clear.
Main dish influence each other from the general case, a motherboard with only two IDE interfaces, each interface can be linked to two IDE devices. But with an interface of the two devices are sharing the bandwidth, the speed of impact is very large. So a little common sense, will separate the two IDE hard drives and optical cable to the motherboard so, IDE has a big problem is that although a board can connect up to four devices, but in fact as long as more than two, the speed greatly reduced.
Bigger problem is the same line two devices must strictly follow the master / slave setup to run properly. Western Digital, as this figure WD400 JB, the main hard drive there are two different settings, one IDE cable connected the hard drive only when pressing the right setting, with the time from the disk is set according to the middle way. According to personal experience, if not brought from the disk and set up by the middle of the way, there will be a wide variety of puzzling questions - sometimes start and sometimes reports can not find the hard drive, and sometimes during startup disk errors and the like report - - Every time you start a different problem that may arise.
Not support hot plug support Parallel ATA devices in the limited ability to hot swap, which is the application server is very important. Because the server usually RAID approach any one hard drive fails you can hot plug replacement, without affecting data integrity, ensure that the server normally open under any circumstances. Hot swap support for SCSI and Fibre Channel accounted for almost all enterprise applications market, the price advantage of parallel ATA and not merely having access to a place, mainly because it does not support hot-swappable.
The error checking is not perfect introduction of technology-based Ultra DMA CRC packet error detection, the technology is ATA-3 standard components. However, there is no standard to provide a parallel ATA commands and status packet error detection. Although the command and the scope and stateful packet error probability is small, but their risk of error can not be ignored.
5 volts using outdated aspects of the processor core requirements from the transition to a low voltage. Lower voltage allows faster signal sudden change, which is to improve speed and reduce the heat loss is essential. Now almost all of the CPU core voltage is less than 2 volts, in order to maintain other chips on the motherboard and system interoperability, typically 3.3 volts separate external voltage, 5 volts to become outdated standards. Although most current ATA/ATAPI-6 standard parallel ATA devices for the specified DC voltage supply 3.3V (± 8%), but some models of the receiver is greater than 4 volts, so using outdated 5 volts.
Interface speed scalability poor addition, Ultra ATA is limited by the characteristics of the parallel bus bandwidth limitations are vulnerable, after several upgrades, the highest transfer rate is only 133M bytes / sec.
SATA IDE is superior than in what place?
SATA no longer use the obsolete parallel bus interface, to switch to a serial bus, the whole style changed completely.
Compared with the original IDE SATA many advantages, most notably from the 80 pin data cable into a 7 pin, and the IDE cable length can not exceed 0.4 meters, while SATA cables can be up to 1 meter, the installation more convenient, conducive to chassis cooling. In addition, it also has many advantages:
One to one connection, there is no master and slave disk troubles with each device is directly connected to the motherboard, exclusive of 150M bytes / sec bandwidth, the speed between the device will not affect each other.
Supports hot-swap hot-plug for the average home user may be of little use, but the server is crucial. In fact, SATA on the low-end server applications, the success of the family than in the general application of the influential.
SATA data transfer more reliable ability to improve error checking, in addition to the CRC error detection data, the will of command and status packets error detection, and therefore improve access compared to parallel ATA's overall accuracy, the string line ATA RAID and external storage in the enterprise applications more attractive.
Low-voltage signal of SATA signal voltage maximum of 0.5 volts, low voltage on the one hand to better adapt to the new platform emphasizes 3.3 volt power supply trend, the other will help speed increases.
SATA bandwidth upgrade potential is not dependent on the system bus bandwidth, but the built-in clock. This generation has just launched 1500MHz SATA internal clock can reach 150M bytes / s interface bandwidth. No longer dependent on the system bus frequency, each generation SATA upgrade to increase bandwidth is doubled: the next generation of 300M bytes / sec, and then the next generation can reach 600M bytes / sec
SATA still exist some shortcomings in the country, people now buy IDE SATA I am afraid to buy a lot more people. There are three major reasons:
First, SATA many advanced PC users, on the whole not too significant, but its greatest significance is adapted to the needs of entry-level enterprise applications.
Secondly, nForce4, 915 of those before the board with SATA hard disk, install the operating system when the need to use floppy disks, hard drives as SCSI, as the trouble of adding a user.
In addition, the domestic relative backwardness of the user's computer configuration, a lot of people are high-capacity hard drive to upgrade the old computer, a little old point motherboard does not support SATA drives.
So, SATA greatest success is attracting a lot of low-end entry-level server users. However, in enterprise applications, it still needs to be improved in many ways:
Single-threaded, only a mechanical chassis SATA ATA, its mechanical chassis is designed for the 8x5 thread, and SCSI-24x7 multi-threaded mechanical chassis is designed to better meet the needs of multi-tasking server. So SATA Although single-task test in poor than SCSI, but the face of a large throughput of the server, or a gap. In addition to speed, the face of multi-task data read, the hard drive head swinging back and forth frequently, so that overheating is a SATA hard drive the biggest problem.
Nominal hot-swap function in practical applications, RAID disk array is composed of multiple hard drives, you must know exactly what a bad hard drive, hot swappable replacement makes sense. Although you can hot-swappable SATA hard drive, but an array of SATA drives in a block when the damage can not be like SCSI, FC and SAS, as with SAF-TE mechanism with light display, know exactly what a bad, hot drawing plug replacement, if the hard disk is removed, it is easy to make the data error. So in practical applications, SATA hot-swappable feature is a bit useless taste.
SATA is slow compared to SCSI and FC slow, mainly due to different mechanical chassis, not suited to the application server requests a large number of non-linear reading. So SATA hard drive to do good video download server, used in the online trading platform is powerless.
SATA 1.0 controller transfer rate is not efficient, although the nominal with a 150MB / s peak rate, in fact, the fastest SATA hard drive speed is only 60MB / s.
Although the price is not the whole solution relative to the SCSI hard disk SATA hard drive is very cheap, but the whole of the SATA solution is not cheap. The main reason is SATA 1.0 controller interface can only connect a hard drive, 8 disk array consisting of 8 required interfaces, each interface 300 to the cost included, is not cheap.
SATA II and SATA II standards
Many people now are not very clear compared to SATA and Ultra ATA What is the difference and benefits, it is no wonder. Because even when the SATA Intel has just launched, but also did not expect this to individual users and to improve the program, results in the entry-level server and workstation applications such as business prospects of the wider front - and because of this, set up only in 2004 the SATA IO (SATA International Organization).
Introduced in front of so many, is a combination of reality and the official white paper SATA finishing, from which already can be found when it comes to SATA advantages and disadvantages, and more from the business application rather than personal and family point of view of the application.
Now often hear "NCQ hard" and "SATA II hard drive" these two terms, they are the next-generation SATA - SATA II development of two different stages of the product:
The first stage is based on adding the SATA NCQ Native Command Queuing, enclosure management (Enclosure Management), backplane interconnect, data scatter / gather of these four new features.
The second stage is the base of the first stage to make further improvements, added dual host active fail-over, with more efficient hard drive connection, 3.0Gb (ie 300MB / s) interface bandwidth and other features.
"NCQ hard drive" of the improvement: not just as simple as SATA II NCQ first phase of several improvements, NCQ Native Command Queuing technology to the larger significance of individual users, so it is more than just a technical understanding of this. In fact, the first phase of adding SATA II technology includes the following items:
NCQ Native Command Queuing Native command queuing: What is NCQ it? This is a SCSI long used a technique only recently applied to SATA drives.
Traditional desktop hard drives with linear forms to process the request, very good potential in this way, we should understand the principles of the physical structure of the hard drive must have a basic understanding. Inside is a hard disc-shaped, much like CD-ROM. Each disc consists of many concentric circles divided into a section of track, track and separate sectors. Each disc is responsible for one or more read heads. If the data is distributed in the same track, looking for the fastest data speeds. Move between the different tracks are consuming a lot of time. Suppose you want to read the three data, one in the outermost track on the disc, one in the innermost track on the disc, as well as one in the outermost track on the disc. Traditional hard drives, in turn reads the disc before the most out of data, and then read the data inside, and finally back to reading the most out of data. As a result, consumption of moving the heads to move the seek time and more efficiency on low. If the head movement and minimize the seek time would be reduced. This is where the purpose of NCQ - NCQ can rearrange the order, not to move inside and then head outside to move from outside, but in the inner disc toward the outer ring of the two before the read data.
Now everyone should understand, CPU speed on the hard drive performance impact is minimal, but the NCQ technology can significantly improve disk performance, especially for the previously mentioned poor performance SATA multi-threaded, easy to swing the head back and forth frequently, these areas are prone to overheating hard disk greatly improved.
Rack Management (Enclosure Management)
The aforementioned hot-swappable SATA technology, the array has a hard drive failure, do not know specifically what a bad and useless. The first stage of SATA II SATA drives with NCQ technology, joined the rack management techniques, is used to solve this problem.
Backplane interconnect (Backplane Interconnect)
SATA cable for data transmission of the number of small, so we had to use an external RAID deployment floor.
The floor is a physical circuit board, usually integrated into the rear of the rack panel, carved above the embedded circuit board by wires to a central controller plug-in connector for multiple devices. It is noteworthy that the central controller and the host interface protocol can be any of the design can be SCSI, Fibre Channel or iSCSI. The use of floor joints and enables the device to bite closely.
Of course, the signal attenuation by the FR4 material constraints, the central controller and the SATA device connection between the etched lines must be limited to the maximum length of 18 inches or less. Although this restriction limits the floor terminal on the surface and SATA rack design, and in fact, the standard rack is 19 inches wide, so in a 1U to 3U of rack for SATA and the maximum cable length is sufficient to etch a convenient location from the center of all the devices connected to the controller connector.
SATA II is not equal to 300MB / s
First, the interface bandwidth from the original 150MB / s extended to 300MB / s. But not with SATA II 300MB / s equate, because it contains the first phase of the NCQ SATA II technology, and more of the other techniques:
Second, SATA II through Port Multiplier, so that each can be connected to a SATA interface hard disk 4-8, that the motherboard has 4 SATA ports, you can connect up to 32 hard drives.
In addition, there is a very interesting technology, called Dual host active fail over. It interfaces via Port Selector selector, connected to two hosts at the same time a hard drive. Thus, when a host fails, when another backup machine to take over yet as the hard disk arrays and data integrity, which ensures that the server regardless of the damage a hard drive or a bad CPU damage like other parts of He was able to function properly.
Conclusion: to prompt PC users especially the last, I believe we IDE, SATA, NCQ, SATA II has been more overall understanding. Maybe a lot of server-side technology is not yet understood, in fact, it does not matter, the most important thing is to obtain such a concept: SATA, SATA II improvements, most are not for personal computer users of the word.
SATA on the PC where the user actually makes sense, that is more favorable for chassis cooling. At the same time, if your motherboard does not support SATA II, to obtain a benefit in the same time, the installation of windows operating system would be more trouble - need to insert the SATA driver floppy disk. So do not think that SATA IDE users more advanced, more advanced use of SATA hard drive performance will be much improved.
That supports NCQ hard drives, like run a number of users of the program may have improved the speed, and because relatively few head swinging back and forth, the hard disk will live longer, the temperature will be relatively low. But not previously mentioned is a necessary prerequisite is the need to motherboard and hard drive support NCQ technology is applied.
As for SATA II, the only meaningful to the user's personal computer is 300MB / s bandwidth - of course, SATA II NCQ support of all. But do not count on doubling the bandwidth than the original, you can get close to twice the speed of SATA, because the current mainly due to the speed of the hard disk drive data transfer rate within the limit, rather than the interface bandwidth, interface bandwidth increase individual users with the speed of improvement is minimal. Similarly, SATA II benefits - support NCQ and 300MB / s bandwidth, the motherboard must support, the motherboard only supports SATA I SATA II hard drive to use, even "minimal" improvements would not have.
Overall, SATA, NCQ as well as a complete SATA II, the general significance of personal computer users is not very large, their greatest significance lies in enterprise applications as a SCSI, FC outside of the cheaper storage solution - of course if several The price difference is small hard drive, then choose as the most advanced SATA II is correct. Worried that the new technology will mature if there is some unknown defects, continue to select SATA I hard drives and even IDE hard disk, the program is quite good
