SCSI standalone enclosure services is a computer protocol used mainly with disk storage enclosures. It allows a host computer to communicate with the enclosure to access its power, cooling, and other non-data characteristics.

The host computer communicates with one or more SCSI 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) controllers in the enclosure via a SCSI interface which may be Parallel SCSI

Parallel SCSI

Parallel SCSI is one of the interface implementations in the SCSI family. In addition to being a data bus, SPI is a parallel electrical bus: There is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it...

, FC-AL

Arbitrated loop

Arbitrated loop, also known as FC-AL, is a Fibre Channel topology in which devices are connected in a one-way loop fashion in a ring topology. Historically it was a lower-cost alternative to a fabric topology. It allowed connection of many servers and computer storage devices without using then...

, 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,...

, or SSA

Serial Storage Architecture

Serial Storage Architecture is a serial transport protocol used to attach disk drives to servers. It was invented by Ian Judd of IBM in 1990...

. Each SES controller has a SCSI identity (address) and so can accept direct SCSI command

SCSI command

In SCSI computer storage, a command is the basic unit of communication. 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 and Serial Attached SCSI....

s.

Implemented commands

The following SCSI commands are implemented by standalone enclosure services devices:

SCSI command	Operation code	Comment
ACCESS CONTROL IN	86h	Optional
ACCESS CONTROL OUT	87h	Optional
CHANGE ALIASES	A4h	Optional
INQUIRY SCSI Inquiry Command The SCSI Inquiry command is used to obtain basic information from a target device. The CDB structure is:If the EVPD parameter bit is zero and the Page Code parameter byte is zero then the target will return the standard inquiry data, which is structured as follows:The special fields in the...	12h	Mandatory
LOG SELECT SCSI Log Select Command The SCSI Log Select command "provides a means for an application client to manage statistical information maintained by the SCSI target device about the target device or its logical units"...	4Ch	Optional
LOG SENSE SCSI Log Sense Command The SCSI Log Sense command is used to obtain current data from log pages in a SCSI target device. The CDB structure for the Log Sense command is:The special parameter fields in the CDB have the following meaning:...	4Dh	Optional
MAINTENANCE IN	A3h	See note 1
MAINTENANCE OUT	A4h	See note 1
MODE SELECT SCSI Mode Select Command The SCSI Mode Select command is used to modify device information contained in mode pages in a SCSI target device. There are two different versions of the command, a 6 byte version and a 10 byte version....	15h/55h	Optional
MODE SENSE SCSI Mode Sense Command The SCSI Mode Sense command is used to obtain current device information from mode pages in a SCSI target device. There are two different versions of the command, a 6 byte version and a 10 byte version.The CDB structure for the Mode Sense command is:...	1Ah/5Ah	Optional
PERISTENT RESERVE IN	5Eh	Optional
PERSISTENT RESERVE OUT	5Fh	Optional
READ BUFFER	3Ch	Optional
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...	1Ch	Mandatory
REDUNDANCY GROUP IN	BAh	See note 1
REDUNDANCY GROUP OUT	BBh	See note 1
REPORT ALIASES	A3h	Optional
REPORT DEVICE IDENTIFIER	A3h	Optional
REPORT LUNS	A0h	Mandatory
REPORT PRIORITY	A3h	Optional
REPORT SUPPORTED OPERATION CODES	A3h	Optional
REPORT SUPPORTED TASK MANAGEMENT FUNCTIONS	A3h	Optional
REPORT TARGET PORT GROUPS	A3h	Optional
REPORT TIMESTAMP	A3h	Optional
REQUEST SENSE SCSI Request Sense Command The SCSI Request Sense command is used to obtain sense data from a target device.The CDB structure is:The response is a set of SCSI sense data which is structured as follows:...	03h	Mandatory
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:...	1Dh	Mandatory
SET DEVICE IDENTIFIER	A4h	Optional
SET PRIORITY	A4h	Optional
SET TARGET PORT GROUPS	A4h	Optional
SET TIMESTAMP	A4h	Optional
SPARE IN	BCh	See note 1
SPARE OUT	BDh	See note 1
TEST UNIT READY SCSI Test Unit Ready Command The SCSI Test Unit Ready command is used to determine if a device is ready to transfer data , i.e. if a disk has spun up, if a tape is loaded and ready etc. The device does not perform a self-test operation. See the Send Diagnostic command....	00h	Mandatory
VOLUME SET IN	BEh	See note 1
VOLUME SET OUT	BFh	See note 1
WRITE BUFFER	3Bh	Optional

Note 1: The initiator

SCSI initiator

In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers ....

needs to send a SCSI inquiry to interrogate the SCCS bit which says whether the SES controller has this command.