SCSI

SCSI

Small Computer System Interface 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...

 Enclosure Services

SCSI Enclosure Services

Most recent SCSI enclosure products support a protocol called SCSI Enclosure Services . The initiator can communicate with the enclosure using a specialised set of SCSI commands to access power, cooling, and other non-data characteristics.-SES devices:...

 (SES) devices contains a number of elements, each of which is defined by a one byte SCSI element code. There are many different element codes defined to cover various devices as shown in the list below.

List of SES element codes

• 00h - unspecified
• 01h - device - disk-drive or other SCSI device
• 02h - power-supply
• 03h - cooling
• 04h - temperature-sensor
• 05h - door lock
• 06h - audible alarm
• 07h - enclosure services controller electronics
• 08h - SCC controller electronics
• 09h - nonvolatile cache
• 0Ah - invalid operation reason - used to determine why an ESI
  Enclosure Services Interface
  The Enclosure Services Interface is a computer protocol used in SCSI enclosures. This is part of a chain of connections that allows a host computer to communicate with the enclosure to access its power, cooling, and other non-data characteristics...
  
   device has failed to complete a command
• 0Bh - UPS
• 0Ch - display
• 0Dh - keypad
• 0Eh - enclosure
• 0Fh - SCSI port/transceiver
• 10h - language
• 11h - communication port
• 12h - voltage sensor
• 13h - current sensor
• 14h - SCSI target port
• 15h - SCSI initiator port
• 16h - simple subenclosure
• 17h - array device
• 18h - SAS
  Serial Attached SCSI
  Serial Attached SCSI is a computer bus used to move data to and from computer storage devices such as hard drives and tape drives. SAS depends on a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in data centers and workstations,...
  
   expander
• 19h - SAS connector
• 1Ah-7Fh - reserved
• 80h-FFh - vendor-specific

How SES elements are used

The SCSI initiator communicates with an SES device using two SCSI commands, Send Diagnostic

SCSI Send Diagnostic Command

The SCSI Send Diagnostic command is used to instruct a target device to perform a self-test on a specific LUN. The CDB structure is:The special parameter fields in the CDB have the following meaning:*PF - Page Format:...

 and Receive Diagnostic Results

SCSI Receive Diagnostic Results Command

The SCSI Receive Diagnostic Results command is used to interrogate the results of a self-test. The self-test must have been triggered by a previous Send Diagnostic command which would have defined the self-test required. This is usually associated with one of the available diagnostic pages.The...

.
The most common SES elements are power-supply, cooling-fan, temperature-sensor and UPS

Uninterruptible power supply

An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...

. The SCSI command protocols assume that there may be more than one of each device type so they must each be given an 8-bit address. When the SES controller is interrogated for the status of an SES element, the response includes a 4-bit status code

SCSI element status codes

When a SCSI SES controller is interrogated for the status of a SES element, the response includes a 4-bit SCSI element status code. The list of valid codes is:*0h - unsupported - status detection is not implemented for this element...

. The most common element status codes are: 1h=OK, 2h=critical, 3h=warning, 5h=not installed.

See the SES

SCSI Enclosure Services

Most recent SCSI enclosure products support a protocol called SCSI Enclosure Services . The initiator can communicate with the enclosure using a specialised set of SCSI commands to access power, cooling, and other non-data characteristics.-SES devices:...

article for a more detailed description.