Failure, capacity and speed of various RAID types for 10 disks Speed relative to 3-disk parity (P) or single disk (S), assuming striping doubles virtual disk speed and mirroring halves it. One may estimate that 1xP = 1.5xS. | No-risk failures | Risk of next failure | Capacity | Speed --------------------------------------------------------------------------- 0 | 0 | 100 | 1 | 10S 1 | 9 | 100 | 1 | 1S 5 (6) | 2 | 100 | 4 | 1P (1.5S) 5 (6R) | 6 | 100 | 4 | 1P (1.5S) 0+1 | 1 | 56 | 2 | 5S 1+0 | 1 | 11 | 2 | 5S 0+5 (6) | 1 | 80 | 2 | 2SP (3S) 0+5 (6R)| 5 | 80 | 2 | 2SP (3S) 0+5 (9) | 1 | 75 | 2 | 3SP (4.5S) 0+5 (9R)| 2 | 75 | 2 | 3SP (4.5S) 5+0 (6) | 1 | 40 | 2 | 2SP (3S) 5+0 (6R)| 2 | 40 | 2 | 2SP (3S) 5+0 (9) | 1 | 25 | 2 | 3SP (4.5S) 5+0 (9R)| 2 | 25 | 2 | 3SP (4.5S) Number in parentheses is number of disks in array. The rest are hot swaps. An "R" indicates post-rebuilding -- this assumes that there is enough time between failures to rebuild a hot-swappable spare. -- Donnie Berkholz