----- "Grant McWilliams" <grantmasterflash@gmail.com> wrote:

> On Wed, Dec 2, 2009 at 9:48 PM, Christopher G. Stach II <
> cgs@ldsys.net > wrote:
>
> ----- "Grant McWilliams" < grantmasterflash@gmail.com > wrote:
>

> > a RAID 10 (or 0+1) will never reach the write... performance of
> > a RAID-5.
>
> (*cough* If you keep the number of disks constant or the amount of
> usable space? "Things working" tends to trump CapEx, despite the
> associated pain, so I will go with "amount of usable space.")
>
> No.
>
> --
> Christopher G. Stach II
>
> Nice quality reading. I like theories as much as the next person but
> I'm wondering if the Toms Hardware guys are on crack or you disapprove
> of their testing methods.
>
> http://www.tomshardware.com/reviews/external-raid-storage,1922-9.html

They used a constant number of disks to compare two different hardware implementations, not to compare RAID 5 vs. RAID 10. They got the expected ~50% improvement from the extra stripe segment in RAID 5 with a serial access pattern. Unfortunately, that's neither real world use nor the typical way you would fulfill requirements. If you read ahead to the following pages, you have a nice comparison of random access patterns and RAID 10 coming out ahead (with one less stripe segment and a lot less risk):

http://www.tomshardware.com/reviews/external-raid-storage,1922-11.html
http://www.tomshardware.com/reviews/external-raid-storage,1922-12.html

--
Christopher G. Stach II