vSAN ESA — FTT=2 Capacity Calculator
Interactive calculator for both FTT=2 protection modes on vSAN ESA: non-stretched RAID-6 (single site) and stretched PFTT=1 + SFTT=1 (two sites + witness).
Cluster Configuration
8
4
4.0 TB
5%
1.5×
9
4
4.0 TB
5%
1.5×
Protection Model
RAID-6 (4+2 Erasure Coding)
Data split into 4 equal chunks + 2 independent parity chunks. Any 2 chunks can be lost. Each chunk lands on a different host (fault domain). Overhead: 1.5× raw.
Data split into 4 equal chunks + 2 independent parity chunks. Any 2 chunks can be lost. Each chunk lands on a different host (fault domain). Overhead: 1.5× raw.
Erasure coding layout
PFTT=1 (inter-site) + SFTT=1 (intra-site)
Site A holds 2 copies of every object (SFTT=1 mirror). Site B holds 2 more (PFTT=1 site mirror). Witness at Site W holds metadata quorum only. Overhead: 4× raw.
Site A holds 2 copies of every object (SFTT=1 mirror). Site B holds 2 more (PFTT=1 site mirror). Witness at Site W holds metadata quorum only. Overhead: 4× raw.
Data copy distribution
Capacity Summary
Usable Capacity
—
after RAID-6 + compression
Raw Pool
—
all drives × all hosts
Effective / VM storage
—
usable × compression
Overhead consumed
—
parity + metadata
Host Sizing
| Policy | Min hosts | Overhead | Survive | Rebuild? |
|---|
Capacity per Site
Total Usable
—
both sites combined
Raw Pool
—
both sites (Site W excluded)
Effective / VM storage
—
usable × compression
Overhead consumed
—
4× mirroring + metadata
Site Breakdown
Failure Tolerance
| Scenario | PFTT | SFTT | Copies | Overhead |
|---|
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