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

Grant McWilliams grantmasterflash at gmail.com
Thu Dec 3 13:09:09 UTC 2009

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:
> > Interesting thoughts on raid5 although I doubt many would agree.
> That's okay. We all have our off days... Here's some quality reading:
> http://blogs.sun.com/bonwick/entry/raid_z
> http://www.cyberciti.biz/tips/raid5-vs-raid-10-safety-performance.html
> http://www.miracleas.com/BAARF/RAID5_versus_RAID10.txt
> http://www.miracleas.com/BAARF/1.Millsap2000.01.03-RAID5.pdf
> http://www.codinghorror.com/blog/archives/001233.html
> http://web.ivy.net/carton/rant/ml/raid-raid5writehole-0.html
> Maybe you are thinking of RAID 6.
> > I don't see how the drive type has ANYTHING to do with the RAID
> > level.
> IOPS, bit error ratio, bus speed, and spindle speed tend to factor in and
> are usually governed by the drive type. (The BER is very important for how
> often you can expect the data elves come out and chew on your data during
> RAID 5 rebuilds.) You will use those numbers to calculate the number of
> stripe segments, controllers, and disks. Combine that with the controller's
> local bus, number of necessary controllers, host bus, budget, and other
> business requirements and you have a RAID type.
> > 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.


Grant McWilliams

Some people, when confronted with a problem, think "I know, I'll use
Now they have two problems.
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