{
  "slug": "placement-group",
  "term": "Placement group (Ceph)",
  "aliases": [
    "Ceph placement group",
    "PG"
  ],
  "definition": "In Ceph, a placement group is a logical grouping of objects within a pool that share storage placement and are managed together for replication and recovery.",
  "note": "Ceph maps objects to placement groups and maps those groups to Object Storage Daemons (OSDs). [ceph-glossary] One OSD can hold data from many placement groups, so a placement group is not a dedicated physical disk or a failure domain. More placement groups can improve distribution but consume CPU, memory and network resources. [ceph-pg]",
  "related": [
    "failure-domain",
    "crush-placement",
    "ceph-up-set",
    "ceph-acting-set",
    "ceph-peering"
  ],
  "citations": [
    {
      "id": "ceph-pg",
      "title": "Ceph Squid documentation: Placement Groups, use and resource costs",
      "url": "https://docs.ceph.com/en/squid/rados/operations/placement-groups/",
      "accessed": "2026-10-13"
    },
    {
      "id": "ceph-glossary",
      "title": "Ceph Squid glossary: Ceph OSD means Object Storage Daemon",
      "url": "https://docs.ceph.com/en/squid/glossary/#term-Ceph-OSD",
      "accessed": "2026-10-13"
    },
    {
      "id": "hesela-availability",
      "title": "Storage availability and correlated failures: placement boundaries",
      "url": "https://hesela.com/analyses/storage-availability-correlated-failures/",
      "accessed": "2026-10-13"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-13"
}