{
  "slug": "scsi-enclosure-services",
  "term": "SCSI Enclosure Services",
  "aliases": [
    "SES"
  ],
  "definition": "SCSI Enclosure Services (SES) is a SCSI standard for monitoring and controlling supported enclosure components such as cooling, power and drive-slot indicators.",
  "note": "SES manages enclosure conditions, including environmental monitoring and control. It is not an interface for reading and writing user-data blocks. [snia-ses]\n\nsg_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. [sg-ses-man]\n\nElement 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. [sg-ses-man] [sg-ses-guide]\n\nFor 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. [sg-ses-guide]\n\nManagement 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. [wd-data60-ses]",
  "status": "shipping",
  "advantages": [
    {
      "text": "Provides a management interface for supported enclosure environmental conditions.",
      "citationIds": [
        "snia-ses"
      ]
    }
  ],
  "limitations": [
    {
      "text": "Supported pages and usable descriptor names vary; convenient selectors are not universally available.",
      "citationIds": [
        "sg-ses-guide"
      ]
    },
    {
      "text": "Status retrieval and state-changing control are separate operations.",
      "citationIds": [
        "sg-ses-man"
      ]
    }
  ],
  "related": [
    "scsi",
    "disk-shelf",
    "sas-expander"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "snia-ses",
      "title": "SNIA dictionary: SCSI Enclosure Services",
      "url": "https://www.snia.org/education/online-dictionary/term/scsi-enclosure-services",
      "accessed": "2026-11-03"
    },
    {
      "id": "sg-ses-man",
      "title": "sg3_utils sg_ses manual (June 2023 header), DESCRIPTION and indexing options; commit 516129c21d8aa574e3075e908477ca8f5db0fd98",
      "url": "https://github.com/hreinecke/sg3_utils/blob/516129c21d8aa574e3075e908477ca8f5db0fd98/doc/sg_ses.8",
      "accessed": "2026-11-03"
    },
    {
      "id": "sg-ses-guide",
      "title": "Douglas Gilbert, The sg_ses utility (2 August 2026): Indexing; Descriptor Names, Device Slot Numbers and SAS Addresses",
      "url": "https://doug-gilbert.github.io/sg_ses.html",
      "accessed": "2026-11-03"
    },
    {
      "id": "wd-data60-ses",
      "title": "Ultrastar Data60 SES specification, D018-000233-000 Revision 05 (March 2026), sections 1.2, 4.1.1 and 6.2",
      "url": "https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/platforms/ultrastar-data60-hybrid-platform/services-specification-ultrastar-data60.pdf",
      "accessed": "2026-11-03"
    }
  ],
  "updated": "2026-11-03",
  "provenance": [
    "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. [wd-data60-ses]"
  ]
}