Raid Array Calculator

Only used by the nested levels RAID 50 and RAID 60.
Spares are additional to the array members and hold no data.
Space consumed by the filesystem itself, as a percentage of raw usable capacity.
Sustained rebuild speed. Leave at 0 to skip the rebuild-time estimate.
Usable capacity
12 TB
RAID Capacity Calculator
Usable capacity
12
Raw capacity
16
Lost to redundancy
4
Storage efficiency
75 %
Disks that may fail
1
Minimum disks for this level
3
Usable capacity in TiB
10.913936
Read throughput multiplier
3x single disk
Write throughput multiplier
3x single disk
Write penalty (I/O per write)
4
Level characteristics
One disk of parity distributed across members; survives one failure.
Worked out from SNIA Common RAID Disk Data Format Specification and 2 other sources.
Single-parity arrays this large carry meaningful risk of a second failure during rebuild; dual parity is usually recommended.
Drives are sold in decimal TB but operating systems usually report binary TiB, which is why a 4 TB disk shows as about 3.64 TiB.

How this is worked out

3 steps
  1. RAID 5 (single parity) with 4 disks of 4 TB each.
  2. Redundancy consumes the equivalent of 1 disk(s); 3 disks' worth carries data.
  3. Usable = 3 x 4 TB = 12 TB

Results are general information, not financial, tax, legal, medical or engineering advice.