Compared with the hard disk of an ordinary PC, the hard disk used on the server has the following four characteristics.
high speed
The server uses a hard disk that can spin up to 7200 or 10,000 rpm, or even higher; it also comes with a large (typically 2MB or 4MB) write-back cache (obsolete, currently up to 64MB of desktop hard disk cache). !); average access time is relatively short; external transfer rate and internal transfer rate higher, using Ultra Wide SCSI, Ultra2 Wide SCSI, Ultra160 SCSI, Ultra320 SCSI and other standard SCSI hard drives, the data transfer rate per second can reach 40MB, 80MB, 160MB, 320MB.
High reliability
Because the hard disk of the server is running for almost 24 hours, the workload is heavy. It can be said that all hard disk manufacturers have adopted their own unique advanced technologies to ensure data security. In order to avoid unexpected losses, server hard drives can generally withstand 300G to 1000G impact.
Use the SCSI interface
Most of the servers use SCSI/SAS hard disks with large data throughput and very low CPU occupancy (although desktop PCs currently have a lower cpu share of SATA disks, they are obviously not on the same level as SAS disks). SCSI hard disks must be used through SCSI interfaces. Some server boards have integrated SCSI interfaces, some have dedicated SCSI interface cards, and one SCSI interface card can accept seven SCSI devices. This is an IDE interface that cannot be compared (an IDE The interface can only expand two channels and interfere with each other seriously).
Hot swappable
Hot Swap (Hot Swap) is a hard disk installation method supported by some servers. It can pull out or insert a hard disk without stopping the server. The operating system automatically recognizes the hard disk changes. This kind of technology is very necessary for a 24-hour server. Of course, currently, SATA hard drives also have this function. For non-critical services, restarting the server is significantly more cost-effective than hot swapping (the risk of hot plugging and loss of data).