Usable vSAN capacity for VMware Cloud Foundation 9.1 / 9.1.1. Models ESA Auto-RAID (RAID-5 2+1 → RAID-6 4+2 at 6 hosts), zStandard compression, global deduplication, Reserved Capacity (Operations + Host Rebuild), stretched and 2-node topologies — and reports binary TiB the way the vSAN UI does. OSA and VCF 9.0 / vSAN 8 models are still available for existing clusters.
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Disclaimer: Capacity figures are estimates based on standard vSAN overhead formulas. Actual usable capacity varies based on compression efficiency, CLOM/metadata overhead, performance leg components (ESA), object size, and workload characteristics. Always validate against the official vSAN ReadyNode Sizer before procurement.
Architecture
ESAExpress Storage · VCF 9 default
OSAOriginal Storage · existing clusters
vSAN release ?
Topology ?
Cluster
Hosts ?
Fault domains ?
Disk layout (OSA)
Disk groups / host ?
Capacity disks / DG ?
Capacity disk size ?
Storage pool (ESA)
NVMe devices / host ?
Device size ?
Policy management
Auto-RAIDsystem managed · 9.1+
Manual policiesstorage policy per VM
Space efficiency
Compression ratio ?
Global deduplication 9.1 GA
Cluster-wide, post-process, 4 KB blocks. HCI clusters 3–64 hosts and vSAN storage clusters. Not for stretched or 2-node.
Deduplication ratio ?
Capacity reservation
Reserved Capacity
Legacy slack
Operations Reserve
Headroom for resync, rebalance and policy changes (~5%).
Host Rebuild Reserve
Reserves ≈ one host of capacity (1/N) so a failed host can be rebuilt in full.
Total reserve scales with cluster size — ≈ 30% on 4 hosts down to ≈ 8% on 32 hosts (HRR ≈ 1/N + OR ≈ 5%).
Slack space ?
Legacy fixed-percent model. Modern vSAN uses Reserved Capacity instead.
Protection policies
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