Backup Daemon and Head DB
Parent: MongoDB Ops Manager and Cloud Manager · Published reference · snapshot 2026-10-23 · skill mongodb-cohort-66a976b0eee5
↓ Facts as markdownall context files
Source-anchored research for Backup Daemon and Head DB. Run status: COMPLETED.
These notes link each claim to its source. Some citations identify archived research reports that are no longer hosted on this site. A published reference means the content is available; it does not certify independent review or accuracy.Read the editorial policy and follow the sources before relying on a claim.
Definitions
- In the legacy architecture, the head database is a local copy of the backed-up deployment on the backup server, maintained per replica set or shard and used to produce periodic snapshots. (high confidence) [source]
- Disk (HEAD) Usage is a legacy interface label: for backup-cursor jobs there is no local head database, and the graph instead reflects source-database size statistics. (medium confidence) (verified as of 2026-10-14) [source]
Comparisons and alternatives
- Starting with featureCompatibilityVersion 4.2, Ops Manager uses backup cursors instead of head databases; legacy full-head-copy requirements must not be generalized to these backups. (high confidence) [source]
- Severalnines' article, updated February 22, 2024, describes encryption of legacy head-database backup jobs using MongoDB Enterprise, WiredTiger, and FCV 3.4 through 4.0; this is historical scope rather than a current support matrix. (low confidence) [source]
- A historical Ops Manager v2.0 Stack Overflow thread reports 'server syncStore is full' despite available disk space. Answers propose stalled head processing, missing job binding, or missing MongoDB binaries; these are diagnostic leads rather than a verified universal fix. (low confidence) [source]
Facts and statements
- Eliminating head databases for snapshot creation does not eliminate the backup service: MongoDB still documents snapshot maintenance, grooming, and queryable restore responsibilities. (high confidence) (verified as of 2026-10-14) [source]
- The legacy head directory holds working database files and must be writable by mongodb-mms; Creationline's 2019 walkthrough provisions separate directories for the head database and retained file-system snapshots. (high confidence) [source]
- Creationline's February 2019 walkthrough sizes legacy HEAD storage roughly against the protected cluster's data size and provisions a separate directory for filesystem snapshots. This is historical guidance, not evidence that current cursor-based backups require a full local copy. (low confidence) [source]
- In a firsthand reply dated October 20, 2021 to an Ops Manager v2.0 thread, a user reported that missing MongoDB binaries prevented head database startup and produced the misleading symptom 'server syncStore is full'. The report does not establish that missing binaries explain every occurrence. (low confidence) [source]
- MongoDB's repository sample configured for Ops Manager 5.0.5 includes spec.backup.headDB.storage separately from oplog and snapshot stores. The presence of this configuration name alone does not demonstrate use of legacy head-database snapshotting. (low confidence) [source]
- The cached Restores reference says the Machine (tries) column includes head DB paths but its retry count applies to obsolete delivery methods; it explicitly says current restore delivery methods do not retry a failed restore. (low confidence) (verified as of 2026-10-14) [source]
- Legacy backups populate the head through initial synchronization and then apply changes from the oplog store to maintain the dataset before scheduled snapshots. (high confidence) [source]
- Removing head databases did not remove the Backup Daemon requirement: the service still supports snapshot maintenance, incremental file-system snapshots, and queryable restore operations. (high confidence) [source]
- The legacy head working copy, snapshot stores, oplog store, and application database serve different purposes: replicated working data, retained recovery images, change history, and operational metadata respectively. (high confidence) [source]
Children
- No children recorded.