n drives and capacity
s of each drive, how would I calculate storage capacity for RAID 2 / 3 / 4?
For example, I know RAID 5's storage capacity can be calculated with the following formula:
(n - 1) * s
A RAID 2 stripes data at the bit (rather than block) level, and uses a Hamming code for error correction. This code uses m parity bits out of 2m - 1 bits therefor the storage capacity for n disks would be 2m - m - 1 where m = log2(n+1). Here are some possible scenarios:
A RAID 3 uses byte-level striping with a dedicated parity disk, so the capacity is (n - 1) * s.
A RAID 4 uses block-level striping with a dedicated parity disk, so again the capacity is (n - 1) * s.