What in the world is SCSI?

Question

Wikipedia has a page for it, but even then the technical definition seemed a bit over my head. Can anyone describe in easier terms for what this is?

Answer 1

This is tricky question, because a number of different technologies have used the SCSI name over the years: SCSI, Ultra-wide SCSI (1 through 3), SCSI (again), iSCSI, and SAS (serial attached SCSI). What they all have in common is they are used in mid to high-end servers for hard drive connections. You can think of it as an alternative to IDE or SATA.

Of all those, only SAS and iSCSI are current. SAS is actually very similar to SATA. The main difference is that it supports hot swapping and that SAS drives are typically more robust (more reserve sectors). iSCSI is a networking specification used for connecting volumes (hard drive/raid paritions) from SAN or NAS devices over the network.

Answer 2

SCSI is a way to connect disks, tape-drives, scanners and other devices to computers. There are several main parts

• SCSI cables
• SCSI connectors
• SCSI host adapters (often a card that plugs into a slot on the motherboard)
• SCSI peripherals (e.g. a SCSI disk-drive)

There are a set of standards that define the cables, the electrical interfacing and the commands that travel over the cables.

SCSI has always been more sophisticated than it's main rival and has therefore been more expensive. SCSI devices generally provide significantly higher performance, longer cables and more devices per controller. Because of the cost, use of SCSI has been mainly restricted to servers and high-performance systems.

Over the years, new versions of the SCSI standards are released. Sometimes there is limited interoperability with devices conforming to a prior SCSI standard.

Answer 3

In plain English, SCSI is a technical spec for storage, usually hard drives and optical drives. As you've noted, there's a description in Wikipedia. SCSI was used in higher end computing equipment, particularly workstations and servers, but was usually more expensive than competing standards, such as IDE, and thus failed to capture significant marketshare.