OpenMetal Large v5 HPC Ceph Usable Storage

Q: How much usable storage does a 3-node Large v5 Hosted Private Cloud Ceph cluster provide?

A 3-node Large v5 Hosted Private Cloud delivers 38.4 TB of raw NVMe capacity, which yields approximately 12.8 TB of usable storage at Ceph’s default 3x replication factor — with per-pool replication tunable to trade durability for usable capacity.

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Each Large v5 node contributes 2x 6.4 TB Micron 7500 MAX NVMe SSDs to the cluster’s Ceph storage pool, for 12.8 TB raw per node and 38.4 TB raw across the 3-node cluster. Ceph manages the OSDs (Object Storage Daemons), replication, thin provisioning, snapshots, and rebalancing across the pool. The default replication factor on production OpenMetal Hosted Private Cloud clusters is 3 — every object is written to three OSDs on three different hosts — which delivers approximately 12.8 TB usable.

Per-pool replication settings let customers trade durability for capacity on workloads where 3x is overkill. For ephemeral build artifacts, cache layers, or compute-checkpoint data that can be regenerated, 2x replication delivers approximately 19.2 TB usable from the same 38.4 TB raw pool. Erasure coding (typically 4+2 or 2+2 profiles on small clusters) can push usable capacity higher still, at the cost of additional CPU overhead and write latency. Most production tenants run a mix: 3x for the default Cinder RBD pool, 2x or erasure-coded for object storage tiers in RGW.

For workloads that outgrow the 3-node Large v5 pool, OpenMetal supports cluster expansion in two directions. Adding more Large v5 compute nodes proportionally grows both compute and storage. Adding dedicated Storage Server nodes (Storage Large v4, etc.) grows storage without adding compute, useful when storage is the bottleneck. Both expansion paths are non-disruptive — Ceph rebalances automatically, OpenStack control plane stays online, tenant VMs continue running. Storage tier additions go through OpenMetal Support; contact them with the target capacity and access pattern to size the expansion.