Is it slower to write one block in RAID Level 5 with 5 disks than RAID 1 with two disks (mirroring only)? I think No since with Level 5 you are writing the data and the parity (two writes). With Level 1, you are writing twice as well (original as well as mirror). Can someone let me know if my train of thought is correct?

  • 1
    I think raid 5 is faster for large transfers, because the pair of disks changes for each block, but if it is just 1 single block it will make no difference, raid5 may even be slower in this case. But who cares if doing little takes a little longer, when doing a lot is faster. – ctrl-alt-delor Aug 7 '14 at 15:54
  • 1
    look here en.wikipedia.org/wiki/Standard_RAID_levels it has figures for read and write performance. The figures look like best-case, ignoring overheads, these overheads could be eliminated using parallel hardware in the disk controller ( a raid controller ). If you do software raid then some of the write performances will be a little worse. – ctrl-alt-delor Aug 7 '14 at 16:03

In RAID-5, unless your write was large enough to cover all data chunks for a given parity chunk, it has to read the missing data chunks in order to be able to recalculate and update parity. Thus a relatively small write on a RAID-5 can turn into a large read operation.

RAID-1 does not need such additional reads, as there is no parity, it just writes to all disks directly. So it's possible that RAID-1 (or RAID-10) is faster for random small writes.

Even so it's hard to tell what's faster or slower overall. It's best if you benchmark it yourself directly for your specific use case scenario.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.