[mythtv-users] Software RAID5 faster than RAID10?

Johnny jarpublic at gmail.com
Mon Apr 13 19:59:16 UTC 2009

On Mon, Apr 13, 2009 at 3:50 PM, Ben Curtis <mythtv at nosolutions.com> wrote:
> Well, unless I'm doing something really wrong in my testing, I've just
> learned that my Software RAID5 is faster at reading and writing than my
> Software RAID10.  Please disprove this if at all possible, as I'm sure this
> will be useful information for anyone setting up a new filesystem for their
> video or system partitions.  Looks like I may be converting my RAID10 to a
> RAID5.  If there are other methodologies I should use to test, let me know
> and I'll be happy to post the results.
> Tested on Fedora Core 10, using 4 500GB drives, split up into multiple
> partitions.  Repeated testing showed pretty much the same results.
> HOWEVER, testing write speeds with a larger file changed the results,
> causing the results to be closer together.

I am no RAID guru but this would make sense to me. With RAID5 you are
writing to 4 drivers in parallel. There is some overhead to calculate
the parity and some additional data written so RAID5 will be slower
than RAID0 with the same number of drives, but with RAID10 you are
basically going to get the same speed as a RAID0 with 1/2 the drives.
So a 4 drive RAID5 beating a 2 drive RAID5 isn't that surprising.
Somebody can correct me if I am wrong, but that is the way I
understand RAID.

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