{
  "slug": "synthetic-full-backup",
  "term": "Synthetic full backup",
  "aliases": [],
  "definition": "A synthetic full backup reconstructs a complete backup for a selected recovery point from retained full and incremental backup data without rereading the entire protected dataset from production.",
  "note": "Synthesis reuses existing backup data. Veeam's documented Hyper-V workflow first takes a new incremental backup, so the overall job still reads recent production changes. [veeam-synthesis]",
  "status": "shipping",
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-14",
  "advantages": [
    {
      "text": "PostgreSQL can use a combined full backup in place of its source chain for a later combination.",
      "citationIds": [
        "combine"
      ]
    }
  ],
  "limitations": [
    {
      "text": "PostgreSQL pg_combinebackup checks chain relationships, not the integrity of every input.",
      "citationIds": [
        "combine"
      ]
    },
    {
      "text": "With pg_combinebackup --link, hard-linked input and output files can affect each other when modified.",
      "citationIds": [
        "combine"
      ]
    },
    {
      "text": "PostgreSQL --no-sync skips the final durability wait; checksum-state changes across inputs can leave invalid page checksums.",
      "citationIds": [
        "combine"
      ]
    },
    {
      "text": "Linux reflinks isolate later writes through copy-on-write but still share underlying storage; they are not independent media copies.",
      "citationIds": [
        "ficlone"
      ]
    }
  ],
  "related": [
    "full-backup",
    "incremental-backup",
    "backup-manifest",
    "backup-verification",
    "restore-test"
  ],
  "citations": [
    {
      "id": "combine",
      "title": "PostgreSQL 18: pg_combinebackup, dependency chains and hard links",
      "url": "https://www.postgresql.org/docs/18/app-pgcombinebackup.html",
      "accessed": "2026-10-14"
    },
    {
      "id": "veeam-synthesis",
      "title": "Veeam Backup & Replication: How Synthetic Full Backup Works (Hyper-V)",
      "url": "https://helpcenter.veeam.com/docs/vbr/userguide/synthetic_full_hiw_hv.html",
      "accessed": "2026-10-14"
    },
    {
      "id": "hesela-backup-evidence",
      "title": "Hesela: Backup verification is not a restore test",
      "url": "https://hesela.com/analyses/backup-verification-is-not-a-restore-test/",
      "accessed": "2026-10-14"
    },
    {
      "id": "ficlone",
      "title": "Linux man-pages: FICLONE, shared storage and copy-on-write isolation",
      "url": "https://www.man7.org/linux/man-pages/man2/FICLONE.2const.html",
      "accessed": "2026-10-14"
    }
  ]
}