RAID Calculator
RAID 10
RAID 10
Striped mirrors. Each pair is RAID 1, then RAID 0 across pairs. The fastest traditional RAID for IOPS workloads — at the cost of half the raw capacity.
How it works
Drives are grouped into mirror pairs (RAID 1). Data is striped across the pairs (RAID 0). Each block exists on exactly two drives. A drive can fail in any pair without data loss. Rebuilds are fast because only the surviving partner is read.
Formula: (N / 2) × min(pair)
Pros / Cons
Pros
- Excellent random read AND write IOPS
- Survives 1+ failures per mirror pair (potentially many across the array)
- Fast rebuilds — only copies the surviving partner
- Simple mental model
- No parity write penalty
Cons
- Halves total capacity (50% efficient)
- Even drive count required
- Capacity-inefficient vs RAID 6
- Pair-coupled failure: both drives in one pair = data loss
When to use
VMs, busy databases, high-IOPS workloads. Production app servers. Anywhere write IOPS matters more than capacity.
When NOT to use
Bulk storage / archives — RAID 6 or RAIDZ2 buy you safety with less overhead. Tiny budgets — too much capacity overhead.
Rebuild math example
8 × 8 TB in RAID 10 (4 pairs). After one drive fails: reads its partner (8 TB) at 70 MB/s ≈ 8 hours. URE probability stays low because only one drive is read.