Archived
beatzaplenty
24a0047fa8
Simplifies the storage model to one long-term tier (Ceph) instead of two. Node 1 runs local ZFS only until nodes 2/3 join, at which point Ceph goes live and VMs migrate onto it directly.
62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
# Storage: LVM-thin → ZFS → Ceph
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## Why move off LVM-thin
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Neither ZFS nor LVM-thin is shared storage — both are node-local. HA needs
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a VM's disk reachable from more than one node so it can restart elsewhere
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on host failure. LVM-thin has no answer for that. Ceph does, natively.
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## Storage model: single node → 3-node cluster
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No intermediate "ZFS + replication" HA step. The plan is deliberately a
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single storage model at the end (Ceph), not two to operate long-term:
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- **Single node (node 1 only)**: local ZFS pool, no cluster-wide HA. This
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is a temporary state, not a design to build tooling around.
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- **3 nodes with Ceph live**: VMs run on Ceph-backed storage — true
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distributed, synchronous storage across all nodes, near-zero RPO on
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failover. Needs 3+ nodes and a fast dedicated network (see
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`03-networking.md`), which is exactly why it can't exist before then.
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## Migration plan (old hardware → new hardware)
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Don't convert the old LVM-thin box in place. Rebuild fresh on new
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hardware with ZFS from the installer (mirror if 2+ disks), then move VMs:
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1. On the old host: `vzdump` each VM to a backup file (external drive,
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NFS share, or PBS if available).
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2. Copy backups to the new host.
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3. `qmrestore` onto the new ZFS storage — disks land as ZVOLs.
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Alternative if both hosts can see each other on the network: temporarily
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cluster them and use the GUI "Migrate" with a storage move (offline only
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— live migration doesn't cross storage types).
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## Standing up Ceph once nodes 2 and 3 exist
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1. Wipe the temporary local ZFS pool on the Ceph-earmarked disks (see
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`01-hardware-node1.md`) on all 3 nodes — they need to end up raw,
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unformatted.
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2. Install the Ceph packages on all 3 nodes (`pveceph install`) and
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initialize the cluster (`pveceph init`), using the dedicated Ceph
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network from `03-networking.md`.
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3. Create Ceph monitors and managers (3 mons for quorum, matching node
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count).
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4. Create OSDs directly on the raw disks on each node — no ZFS/RAID
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underneath.
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5. Create a Ceph pool sized for your VM storage needs (replica count,
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typically 3 for full redundancy across 3 nodes).
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6. Add the pool as PVE storage (RBD), then migrate VMs from local ZFS
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onto it — offline migration if crossing storage types, or storage
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migration via the GUI.
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7. Configure HA groups once VMs are on Ceph-backed storage.
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## Notes
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- Ceph RAM/CPU overhead is real — budget per `01-hardware-node1.md`
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(roughly 3-5GB RAM and a core per OSD, on top of VM workloads).
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- Enterprise SSDs with power-loss protection (PLP) matter far more here
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than for plain ZFS — Ceph write latency is sensitive to it.
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- Once Ceph is live, local ZFS remains only for each node's boot pool —
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it's not a fallback tier for VM storage going forward.
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