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Date: Wed, 28 May 2008 12:54:11 +0200
From: Peter Rabbitson <rabbit+list@rabbit.us>
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To: Justin Piszcz <jpiszcz@lucidpixels.com>
CC: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)
References: <alpine.DEB.1.10.0805280442330.4527@p34.internal.lan>
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Justin Piszcz wrote:
> Hardware:
> 
> 1. Utilized (6) 400 gigabyte sata hard drives.
> 2. Everything is on PCI-e (965 chipset & a 2port sata card)
> 
> Used the following 'optimizations' for all tests.
> 
> # Set read-ahead.
> echo "Setting read-ahead to 64 MiB for /dev/md3"
> blockdev --setra 65536 /dev/md3

That's actually 65k x 512byte blocks so 32MiB

> # Set stripe-cache_size for RAID5.
> echo "Setting stripe_cache_size to 16 MiB for /dev/md3"
> echo 16384 > /sys/block/md3/md/stripe_cache_size
> 
> # Disable NCQ on all disks.
> echo "Disabling NCQ on all disks..."
> for i in $DISKS
> do
>   echo "Disabling NCQ on $i"
>   echo 1 > /sys/block/"$i"/device/queue_depth
> done
> 
> Software:
> 
> Kernel: 2.6.23.1 x86_64
> Filesystem: XFS
> Mount options: defaults,noatime
> 
> Results:
> 
> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html
> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.txt
> 
> Note: 'deg' means degraded and the number after is the number of disks 
> failed, I did not test degraded raid10 because there are many ways you 
> can degrade a raid10; however, the 3 types of raid10 were benchmarked 
> f2,n2,o2.
> 
> Each test was run 3 times and averaged--FYI.
> 

Results are meaningless without a crucial detail - what was the chunk size 
used during array creation time? Otherwise interesting test :)

Cheers

Peter