In SCSI computer storage, computers and storage devices use a client-server model of communication. The computer is a client which requests the storage device to perform a service, e.g., to read or write data. The SCSI command architecture was originally defined for parallel SCSI buses but has been carried forward with minimal change for use with Fibre Channel, iSCSI, Serial Attached SCSI, and other transport layers.
In the SCSI protocol, the initiator sends a SCSI command information unit to the target device. Data information units may then be transferred between the computer and device. Finally, the device sends a response information unit to the computer.
SCSI commands are sent in a command descriptor block (CDB), which consists of a one byte operation code (opcode) followed by five or more bytes containing command-specific parameters. Upon receiving and processing the CDB the device will return a status code byte and other information.
The rest of this article contains a list of SCSI commands, sortable in opcode or description alphabetical order. In the published SCSI standards, commands are designated as "mandatory," "optional" or "vendor-unique." Only the mandatory commands are required of all devices. There are links to detailed descriptions for the more common SCSI commands. Some opcodes produce different, though usually comparable, effects in different device types; for example, opcode 0x01 recalibrates a disk drive by seeking back to physical sector zero, but rewinds the medium in a tape drive.
service, e.g., to read or write data. The SCSIcommand architecture was originally defined for parallel SCSI buses but has been carried forward with minimal...
SAS-4 in 2017. The SCSI standards define commands, protocols, electrical, optical and logical interfaces. The SCSI standard defines command sets for specific...
act as a SCSI target. SCSI-1 and SCSI-2 have the option of parity bit error checking. Starting with SCSI-U160 (part of SCSI-3) all commands and data are...
appeared in the mid-1980s. SAS, like its predecessor, uses the standard SCSIcommand set. SAS offers optional compatibility with Serial ATA (SATA), versions...
thumb drives. UAS depends on the USB protocol, and uses the standard SCSIcommand set. Use of UAS generally provides faster transfers compared to the older...
In SCSI standards for transferring data between computers and peripheral devices, often computer storage, commands are sent in a Command Descriptor Block...
provides block-level access to storage devices by carrying SCSIcommands over a TCP/IP network. iSCSI facilitates data transfers over intranets and to manage...
SCSI Multimedia Commands (MMC) defines a SCSI/ATAPI based command set for accessing and controlling devices of type 05h. Such devices read or write optical...
returned by a SCSI device. When a SCSI target device returns a check condition in response to a command, the initiator usually then issues a SCSI Request Sense...
In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSIcommand. The initiator usually does not...
A SCSI connector (/ˈskʌzi/ SKUZ-ee) is used to connect computer parts that communicate with each other via the SCSI standard. Generally, two connectors...
devices can be connected to a computer than with the ATA command set alone. It carries SCSIcommands and responses through the ATA interface. ATAPI devices...
early ATAPI devices were simply SCSI devices with an ATA/ATAPI to SCSI protocol converter added on. The SCSIcommands and responses are embedded in "packets"...
ago[ambiguous] and approved for the SCSIcommand set nearly 10 years ago[ambiguous] as "Object-based Storage Device Commands" (OSD), however, it had not been...
initiator can communicate with the enclosure using a specialized set of SCSIcommands to access power, cooling, and other non-data characteristics. There...
device addressed by the SCSI protocol or by Storage Area Network protocols that encapsulate SCSI, such as Fibre Channel or iSCSI. A LUN may be used with...
most drivers only support the SCSI transparent command set, designating their subset of the SCSIcommand set with their SCSI Peripheral Device Type (PDT)...
interfaces. The length limit of the data cable allows for external SCSI devices. The SCSIcommand set is still used in the more modern SAS interface. Integrated...
A SCSI Status Code is used to determine the success or failure of a SCSIcommand. At the end of any command, the target returns a Status Code byte which...
is filled up, the storage unit must be replaced. Compared to ATA, the SCSIcommand set allows finer-grained management of bad sectors. Users can read the...
procedure AMZ Tur, military vehicle Toxics use reduction Test Unit Ready, a SCSIcommand in computer science Tur (Bosnian-Slavic mythology) tur, "there" In Latvian...
"cache flush" commands in the right places, which is usually referred to as the implementation of write barriers. Newer SATA and most SCSI disks can accept...
described before the introduction of SATA as ATA), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel. Bridge circuitry is sometimes used to...
issue SCSIcommands to request services from components, logical units of a server known as a "target". A "SCSI transport" maps the client-server SCSI protocol...
a protocol that transports SCSIcommands over Fibre Channel networks. FICON is a protocol that transports ESCON commands, used by IBM mainframe computers...
the WRITE12 SCSI Write Commands. The line width and number of pixels in each line are set in the LabelTag SCSI mode pages. The WRITE12 command is called...
when a SCSI device needs to report an error. SCSI communication takes place between an initiator and a target. The initiator sends a command to the target...
Global Information