[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.

http://www.tomshardware.com/reviews/external-raid-storage,1922-9.html



Grant McWilliams

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