What is 'SCSI-disk' ?

[Schmidt]

Just learning linux hardware... I read that SCSI bus is a "kind of bus intended to unite different types of devices such a IDE and SATA disks, tape devices and so on". So what means the term 'SCSI-disk' if SCSI is a bus?..

[lugoteehalt]

In practice it just means a hard disk or CD/DVD disk drive with a different sort of plug. ATAPI drives have a wide ribbon cable with an elaborate multipin connector on the end. SATA drives have a much simpler wire with a - I have not counted - simple 4 socket connector on the end. My mother board accommodates both types. SATA is easiest these days. With it you usually call the device /dev/sda instead of the previous /dev/hda.

Hope that's what you were getting at.

[rcgreen]

A SCSI disk will plug in to a SCSI interface. Most common
PCs don't have a SCSI interface on the motherboard, so
there are SCSI cards, if you want to use SCSI. A lot of high
performance PCs do have SCSI, especially those intended
to be servers.
SCSI can also support external devices.

[Schmidt]

then, any disk just connected to SCSI bus is called SCSI-disk?...)

[coopstah13]

SCSI - Wikipedia, the free encyclopedia

i would agree with what you say

[theNbomr]

SCSI is a bus type that is used (seldom these days) for connection of a few different types of devices, not just disks. Tape drives, at least higher-end ones, were almost always connected with SCSI interfaces. There were some scanners that had SCSI interfaces. Disk drives, as some have mentioned, including optical drives. Other 'industrial' backplanes and smart devices have used SCSI interfaces to computers. It was originally the only type of disk supported in Unix, and many traits of modern filesystems (like block-oriented access) derive from the SCSI interface.
--- rod.

[MASONTX]

SCSI is a standard format for accessing hardware, just as other standards define how devices like USB connect to the computer. A hard drive, cd, or othe hardware which uses that standard to connect to your computer is a SCSI hard drive etc.

From the Wiki definition: "Small Computer System Interface, or SCSI (pronounced scuzzy[1]), is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

SCSI is an intelligent, peripheral, buffered, peer to peer interface. It hides the complexity of physical format. Every device attaches to the SCSI bus in a similar manner. Up to 8 or 16 devices can be attached to a single bus. There can be any number of hosts and peripheral devices but there should be at least one host. SCSI uses hand shake signals between devices, SCSI-1, SCSI-2 have the option of parity error checking. Starting with SCSI-U160 (part of SCSI-3) all commands and data are error checked by a CRC32 checksum. The SCSI protocol defines communication from host to host, host to a peripheral device, peripheral device to a peripheral device. However most peripheral devices are exclusively SCSI targets, incapable of acting as SCSI initiators—unable to initiate SCSI transactions themselves. Therefore peripheral-to-peripheral communications are uncommon, but possible in most SCSI applications. The Symbios Logic 53C810 chip is an example of a PCI host interface that can act as a SCSI target."