[CentOS-virt] Slightly OT: FakeRaid or Software Raid

Christopher G. Stach II

cgs at ldsys.net
Thu Dec 3 14:08:35 UTC 2009

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

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


Christopher G. Stach II

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