Snapshot consistency limits on active VMs with Ceph-backed volumes
0 reputation · 29 Apr 2023, 05:50 UTC
Snapshot consistency limits on active VMs with Ceph-backed volumes
Harvester’s snapshot API allows administrators to capture a VM’s disk state for backup and recovery. The API is documented for both local and Ceph‑backed volumes, but the guarantees around block‑level consistency when the VM is actively writing are not explicitly addressed. The retention policy is configurable, yet its impact on storage quota and concurrent snapshot performance remains undocumented. This uncertainty hampers planning for large‑scale snapshot operations, especially when multiple VMs share Ceph storage.
Key constraints include active I/O during snapshot, the choice of storage backend, and the configured retention window. The main uncertainty is whether snapshots preserve a consistent block state on Ceph and how retention interacts with storage limits.
Specific questions:
- Does the /snapshots endpoint guarantee block‑level consistency for Ceph‑backed volumes when a VM is actively writing?
- How does the retention policy affect storage quota and performance during concurrent snapshot operations on Ceph?
- What safeguards, if any, does Harvester provide when a VM with pending snapshots is live‑migrated?
