RAID 60 Calculator
RAID 60 stripes across multiple RAID 6 sub-arrays, combining dual parity's fault tolerance with better scaling for very large disk counts.
The RAID 60 formula
Usable Capacity = (Disks per sub-array − 2) × Number of sub-arrays × Disk Size
This calculator assumes 2 equal sub-arrays. Each sub-array is its own RAID 6 set with double parity; the outer layer stripes across them like RAID 0.
Worked example
8 disks × 4 TB, split into 2 sub-arrays of 4 disks each = 16 TB usable out of 32 TB raw (50% efficiency), guaranteed to tolerate 2 disk failures per sub-array (up to 4 total across the array, as long as no single sub-array loses more than 2).
When RAID 60 earns its capacity cost
Very large arrays (16+ disks) where a single wide RAID 6 array would still have an uncomfortably long rebuild window. Splitting into RAID 6 sub-arrays contains rebuild impact to one sub-array at a time and improves overall fault tolerance, at a real capacity cost — 4 disks' worth of overhead in the worked example above versus 2 disks' worth for a single RAID 6 array on the same 8 disks. Like RAID 50, this needs a controller or software RAID stack with explicit nested-level support.
What's the minimum number of disks for RAID 60?
8 disks (2 sub-arrays of 4, the minimum size for RAID 6).
Is RAID 60 overkill for a typical server?
For most workloads under 12-16 disks, a single RAID 6 array is simpler and more capacity-efficient with nearly the same protection. RAID 60 earns its keep specifically on large, wide arrays where a single RAID 6 rebuild window becomes a real operational risk.
Need a different RAID level? Use the full RAID Calculator covering RAID 0, 1, 5, 6, 10, 50, 60 and ZFS RAIDZ1/2/3, or read the RAID levels comparison guide.