Analysis of SCSI and SATA Selection

Administrators  often need to face the option of choosing to use an updated, more  exciting technology or choose to use existing technology that has proven  to be stable. For our server hardware devices, these two options are specific to  whether to use a new SATA hard drive or an existing SCSI drive.

Price factors and some new features make serial ATA, that is what we call SATA technology is very attractive. But it seems to me that the use of SCSI technology is still a good  standard for the server, I will tell you the reasons in this article.

SATA  technology is an upgraded version of the existing ATA / IDE drive  standard, which has been used for many years as a standard for desktop  hard drives and removable storage devices such as CD / DVD drives. Compared to SCSI drives, ATA drives always have a low price and ease of use, just behind performance in SCSI drives. While SATA technology has been to narrow the performance gap as the  goal, and provides a lot of compelling features, it can be said, SATA  technology in performance has taken a big step.

SATA cables STC technology advantages

SATA is cheaper than SCSI. Whether it is the drive or the hardware itself (such as controllers and data lines), are much cheaper than SCSI. If you have to consider the budget needed to build a server, then this is a very attractive point. In  most cases, building a redundant array of SATA-based inexpensive disks  is much less expensive than building a SCSI array of the same capacity. For example, a 36-GB, 10,000-rpm enterprise-class SCSI drive costs $  175, and the same cost can be purchased with a capacity of 200 GB, 7,200  RPM SATA drives per minute.

SATA provides almost the speed comparable to SCSI. Under  ideal conditions, SATA-based redundant array of inexpensive disks can  reach 90 percent to 95 percent faster than SCSI-based arrays. And a single SATA drive is almost able to achieve this standard.

From a physical point of view, SATA management easier. SATA drives use data and power connections that are lighter and easier to manage than those used by SCSI drives. SATA data cable required length is generally not more than one meter,  this will not cause signal transmission problems, and thinner data lines  can also bring more air to the equipment space.

Use the benefits of SCSI drives

Said the advantages of so many SATA technology, we look at its  shortcomings, it is these shortcomings led to the limitations of this  technology application.

SATA drives have not yet reached the level of enterprise-class SCSI drives. The high power consumption that an enterprise's SCSI drives can afford is that SATA drives can not afford. There  are still some gaps in SATA drives and enterprise-class SCSI drives,  such as data splitting, mechanical errors, and disk errors. In general, SATA drives are considered a desktop-level drive, and  manufacturers can not guarantee that these drives will work for more  than two or three years at high usage levels.

SATA command level is not enterprise-class. SCSI  uses a technique called "command queue" to optimize the storage of  data, which allows the controller to execute requests related to data  within the drive according to the best command. For  a server, at the same time there will be a lot of different users to  make a request, if the disk drive does not have such a similar layer can  handle a lot of concurrent demand technology, then the disk drive will  become a bottleneck in system performance, resulting in System performance degradation. And SATA drives do nothing better in this area than SCSI drives.

SATA technology relies on CPUs to manage data transfers while SCSI drives are not. SATA  technology to ATA / IDE technology on the CPU's dependency completely  inherited down, it uses the CPU to manage the data transmission, this  will increase the CPU occupancy rate. The  SCSI controller can rely on the controller's own hardware devices to  manage data transmission, which means that SCSI drives can have faster  and greater data throughput. Although  SATA technology to the system to bring additional CPU occupancy rate  and the traditional ATA / IDE drive compared to much smaller, but these  CPU occupancy and bus bandwidth can be used to do other things, then why  not What?

SATA drives require a dedicated power connection device. In many cases, this is a small but important factor that should be taken into account when calculating the budget. SATA drives do not work properly without a traditional drive power connection device. While a dedicated SATA power connection device requires a system power  supply cost and the cost of using a power converter is almost $ 10 per  drive.

In  short, the most suitable for using SATA technology is those simple,  single-hard disk servers and desktop computers, or some need to provide  high-speed disk performance of the workstation (such as multimedia  editing station). Although the price of SATA is very attractive, but we'd better not use it in the enterprise-class server. Spend some money on the SCSI device, the rest of the things become simple. SATA  drives will be a compelling alternative to low-level SCSI applications  (such as desktop computers that use SCSI drives), which should gradually  replace the presence of ATA / IDE devices and get a wide range of  applications in this area.