[mythtv-users] Software RAID5 faster than RAID10?

[Raymond Wagner]

From: *Ben Curtis* <mythtv at nosolutions.com <mailto:mythtv at nosolutions.com>>
> Date: Tue, Apr 14, 2009 at 10:49 AM
> Subject: Re: [mythtv-users] Software RAID5 faster than RAID10?
> To: mythtv-users at mythtv.org <mailto:mythtv-users at mythtv.org>
>
>
> > Now the problem is that any read and any write on raid5 must access all
> > the disks, so you end up with roughly the same IOop rate as with a
> > single drive. With raid10, you now have two independent sets of data.
> > You must write to all disks at once, but you can read from either disk
> > in the mirror, doubling concurrent IOops.
> >
>
> This is actually a really good point I hadn't thought of.  In my setup, I
> have a RAID5 for my recordings, and the RAID10 is my system partition
> (which also houses 2 VMWare images that run constantly).  Despite the
> single file read/write times, from an IO perspective, my RAID10 may be
> something I should stick with.
>
>
> Thanks everyone,
> Ben
>
That was a bit of an over-simplification.  Striped arrays (RAID0/5/6) 
typically come with block sizes of 64K or 128K.  You only need to access 
the blocks your data exists on.  If you are only doing small data reads, 
you can have up to 3x the IO performance on a 4-disk array.