SCSI's English name is "Small Computer System Interface", the Chinese translation for "Small Computer System Interface-specific"; it can install other peripherals to the computer equipment to improve system performance or to add new features, such as hard drives, optical drives, scanners and so on.
Performance of personal computers in recent years due to the expansion of demand that the substantial increase in the application of SCSI on the PC more and more.
In fact, SCSI is not considered a new type of interface, from 1986 to formally set the standard since the SCSI has also gone through nearly 20 years. The early pioneers SCSI Apple Mac computer selected as the standard interface.
The PC side because the SCSI interface card and the device is relatively expensive, so SCSI is not the favorite. But now supports SCSI interface peripheral products from only the hard disk, tape two, to scanners, optical drives, burners, MO and other equipment, combined with advances in technology, so now the SCSI market is relatively mature.
We measure the performance of a SCSI hard drive, the main reference to the following indicators:
Spindle speed
Spindle speed is a more important performance parameters, but also determines the internal hard disk transfer rate and sustained transfer rate of the first determining factor. Today, more than the speed of the hard disk is 5400rpm, 7200rpm, 10000rpm and 15000rpm. From the current situation, 10000rpm the SCSI drives have the advantage of cost-effective, but also SCSI hard drive is the mainstream.
Internal transfer rate
The level of the internal transfer rate is to evaluate the overall performance of a decisive factor in the hard disk, hard disk data transfer rate is divided into internal and external transfer rate. External transfer rate is usually known as the burst data transfer rate or interface transfer rate, refers to the cache from the hard drive out of the output data rate. Since the internal hard disk transfer rate is less than the external transfer rate, only the internal transfer rate can only be as a measure of the true hard drive performance.
Platter capacity
In addition to the contribution to the growth of capacity, the single platter, another is to raise the importance of hard disk data transfer speed. Single disc capacity increase due to the increase in the number of tracks and track magnetic linear increase of the density.
Track the increase in the number of head of the seek time for the good for less, because the disk radius is fixed, the increase in the number of tracks means to shorten the distance between tracks, while the head from one track to another track on the required bit time will be shortened.
Average seek time
Average seek time is the head moved to the data track where the time required, it is important to measure the mechanical properties of the hard disk indicator, generally between 3ms ~ 13ms, the proposed average seek time than 8ms of SCSI hard disk will not be considered. Average seek time and average latency time (the decision entirely up to speed) that together determine the hard disk where the cluster head to find the time data. This time directly affects the data transmission speed of random disk.
Cache
Enhance the capacity of the hard disk cache is also a shortcut to improving the overall performance of the hard disk. Because the internal hard disk data transfer speed and the external transmission speed different. Needed to do a speed cache adapter. The size of the cache for the hard drive has a sustained data transfer speed of a great impact.
At present, the mainstream of the server hard disk manufacturers are mainly seagate (Seagate), IBM and so on.