What’s SCSI?

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SCSI is a faster and more robust interface than IDE, used for computer components such as hard drives, optical drives, scanners, and tape drives. It can connect 15 or more devices in a daisy chain, but is more expensive. Different versions have different reference speeds, and it is important to match the correct SCSI controller to the desired components. SCSI can be a great choice for a RAID, but SATA RAID is a good alternative at an affordable price.

SCSI is a type of interface used for computer components such as hard drives, optical drives, scanners and tape drives. It is a competing technology of the standard IDE (Integrated Drive Electronics). While less expensive IDE technology is built into motherboards, SCSI is a technology that must be added by purchasing a special controller. The SCSI card plugs into an internal PCI slot and associated devices are then connected to this card.

This interface is a faster and more robust technology than the IDE and has traditionally been used in servers. Besides speed, another big advantage over IDE is that the card can connect 15 or more devices in a daisy chain. The controller assigns each device its own ID, allowing for great flexibility in expanding any system.

SCSI devices, especially hard drives, are designed to be used 24/7 to meet the needs of the server market. For this reason, the drives are generally built to higher standards and offer longer warranties than IDE drives of comparable capacity. However, the added speed and quality comes at a price. SCSI components are significantly more expensive than their IDE cousins.

As technology has evolved, different varieties have emerged with different reference speeds. The various versions use different pin connectors. Therefore, it is important to match the correct SCSI controller to the desired components. For example, if a drive is Ultra 320, a SCSI-I controller won’t work with it. The controller must support Ultra 320 to be compatible. Below is a list of versions with data rates in megabytes per second (MB/sec):

SCSI-2, fast SCSI (8 bit strict)
a 10 MB/sec

Ultra (8-bit tight)
20 MB / sec

Ultra Wide (16-bit wide)
40 MB / sec

Ultra2 (16-bit wide)
80 MB / sec

Ultra 160 (largo 16 bit)
160 MB / sec

Ultra 320 (largo 16 bit)
320 MB / sec

For a server, SCSI can be a great choice for a redundant array of independent disks (RAID), since you can add more drives as needed. If the wallet cannot afford a SCSI RAID or if, as in the case of an end user, the technology is too much, a SATA RAID is a good alternative at an affordable price.




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