SCSI element codes

SCSI Enclosure Services (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 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 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 and Receive Diagnostic Results. The most common SES elements are power-supply, cooling-fan, temperature-sensor and UPS. 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. The most common element status codes are: 1h=OK, 2h=critical, 3h=warning, 5h=not installed.

See the SES article for a more detailed description.

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
• 1h - OK - element is installed and no error conditions are known
• 2h - critical - critical condition is detected
• 3h - noncritical (warning) - noncritical condition is detected
• 4h - unrecoverable - unrecoverable condition is detected
• 5h - not installed - this element is not installed in the enclosure
• 6h - unknown - sensor has failed or element status is not available
• 7h - not available - element installed, no known errors, but the element has not been set into operation
• 8h-Fh - reserved

References

• StorageSecrets.org - SCSI Enclosure Services (SES & SES-2) Management
• 08-026r0 SES-2 Element control and status nomenclature.fm - T10.org (page 20 and 22)