----- "Grant McWilliams" <grantmasterfl...@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


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