hesela.devSCSI Enclosure Services
SCSI Enclosure Services (SES) is a SCSI standard for monitoring and controlling supported enclosure components such as cooling, power and drive-slot indicators.
SES manages enclosure conditions, including environmental monitoring and control. It is not an interface for reading and writing user-data blocks. [1]
sg_ses retrieves status with RECEIVE DIAGNOSTIC RESULTS and requests changes with SEND DIAGNOSTIC. A dedicated enclosure-services logical unit reports peripheral device type 0x0d; attached services can instead be indicated by EncServ on another device type. [2]
Element index, device slot number and SAS address are different selectors. Low-level indexing follows Configuration-page structure, while the slot number comes from Additional Element Status. The value 255 means no corresponding slot, not bay 255. Descriptor-based selection needs supported pages and usable names. [2] [3]
For a SAS drive, address-based selection uses a target-port SAS address, not necessarily a persistent drive identity. An expander can assign a SATA device an address different from its WWN. Confirm the reported mapping against enclosure documentation before identifying hardware for replacement. [3]
Management reachability does not establish drive availability. In one documented SAS enclosure, the enclosure-services processor can return GOOD to TEST UNIT READY while the enclosure is offline and drives are not presented to hosts. Its status-page replies use last-known observations without forcing immediate polling. These are documented product behaviors, not universal SES timing guarantees. [4]
Relations
- related
- SCSI, Disk shelf, SAS expander
Advantages
- Provides a management interface for supported enclosure environmental conditions. [1]
Limitations
- Supported pages and usable descriptor names vary; convenient selectors are not universally available. [3]
- Status retrieval and state-changing control are separate operations. [2]
Citations
- SNIA dictionary: SCSI Enclosure Services
- sg3_utils sg_ses manual (June 2023 header), DESCRIPTION and indexing options; commit 516129c21d8aa574e3075e908477ca8f5db0fd98
- Douglas Gilbert, The sg_ses utility (2 August 2026): Indexing; Descriptor Names, Device Slot Numbers and SAS Addresses
- Ultrastar Data60 SES specification, D018-000233-000 Revision 05 (March 2026), sections 1.2, 4.1.1 and 6.2
Sources & caveats
- Definition and environmental scope follow SNIA; selector and command details follow the pinned sg_ses manual and the author's dated guide.
- This is a source review, not an enclosure test or a certification that reported identities match physical bay labels.
- The readiness and status-freshness example is specific to Ultrastar Data60, D018-000233-000 Revision 05, sections 1.2, 4.1.1 and 6.2. No hardware experiment was performed. [4]