> Quick question.
> If I have a 6 member RAID 5 array, and a 10 member RAID 10 array (5 mirrors,
> then striped), which is technically faster for both reads & writes? I know
> that in general, more spindles is better for performance. I also know that
> in general, RAID 5 writes take a penalty for computing and writing parity
> across all the drives, at least compared to pure striping (RAID 0). However,
> don't I suffer a write penalty by having to commit 10 writes in my 10 member
> RAID 10 array? I know reading should be faster on the RAID 10 array because
> for each of the stripe members, I have 2 options from which to read my data
> from, and will usually come from the least busy spindle.
> Basically, I'm just looking to settle a bet with myself :). I know there are
> some other factors that go into the above, but assuming the arrays are using
> the same hardware, same disks, and so on, I'm just looking for which should
> give me more 'pure' IO capability.
Well... Bill Todd could probably answer this as good as any
in this forum .. but let me take a low-key stab.
RAID10 will be faster for a number of factors. First, on writes
parity does not have to be calculated , therefore you don't
have to do a read just to write (read in parity information).
Secondly, on reads you will actually have 10 members to read
from versus 6 members of the RAID5.
You could take the time to learn a whole bunch more by going
out to: www.google.com and typing in some relevant keywords,
raid 5 performance comparison
and looking at some good hits, for example:
"Even if the biblical assertion is incorrect that where there is no vision,
the people perish, it is difficult to think what could be the engine or
stimulus for social behavior in a nihilistic system committed only to the
certainty of the passage of time, without any energetic relationship to
another principle or purpose." --Lionel Tiger