[ale] Raid perf?

Jeff Lightner jlightner at water.com
Fri Oct 24 17:58:42 EDT 2008


Other than performance is the fact that RAID10 can actually suffer TWO
disk failures before the raid set goes away.   Haven't worked with RAID6
so don't know its redundancy.

-----Original Message-----
From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Greg
Freemyer
Sent: Friday, October 24, 2008 2:52 PM
To: Atlanta Linux Enthusiasts
Subject: Re: [ale] Raid perf?

All,

If anyone cares I found this Dell doc:

http://www.dell.com/downloads/global/products/pvaul/en/PERC6_PerfWP_WMD1
120.pdf

Per it, Raid 6 is in theory 3 times less efficient than Raid 10 on
writes.

So to maintain the same write performance as my 4-disk Raid 10 I would
need a 12-disk Raid 6.

That is worse than I realized, but feasible for my needs.  (I think
250GB drives are down to $60 or so.  Thus 12 is only $700.  Obviously
I need the controller card too.  Haven't priced that yet.  I do have
big chassis that can hold the drives.)

Time for me to do a better job of characterizing my app to see what
percentage the i/o's are reads vs. writes.

Greg

On Fri, Oct 24, 2008 at 9:53 AM, Greg Freemyer <greg.freemyer at gmail.com>
wrote:
> All,
>
> I have a Raid 10 (4x500GB) under Fedora using software raid that I
> want to replace with a Raid 6 (6x1TB).
>
> Does anyone know a website that will help me understand what the
> impact will be from a write perspective?  Assuming random DB style
> writes, not sequential.
>
> I'm curious about both theoretical and real world  (3ware or linux
> software raid) performance numbers.
>
> Thanks
> Greg
> --
> Greg Freemyer
> Litigation Triage Solutions Specialist
> http://www.linkedin.com/in/gregfreemyer
> First 99 Days Litigation White Paper -
>
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pd
f
>
> The Norcross Group
> The Intersection of Evidence & Technology
> http://www.norcrossgroup.com
>



-- 
Greg Freemyer
Litigation Triage Solutions Specialist
http://www.linkedin.com/in/gregfreemyer
First 99 Days Litigation White Paper -
http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pd
f

The Norcross Group
The Intersection of Evidence & Technology
http://www.norcrossgroup.com
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