Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)

From: Bill Davidsen
Date: Fri May 30 2008 - 08:43:15 EST


Justin Piszcz wrote:


On Thu, 29 May 2008, Holger Kiehl wrote:

On Wed, 28 May 2008, 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

# 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

Why is the Sequential Output (Block) for raid6 165719 and for raid5 only
86797? I would have thought that raid6 was always a bit slower in writting
due to having to write double amount of parity data.

Holger


RAID5 (2nd test of 3 averaged runs) & Single disk added:
http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html

Other than repeating my (possibly lost) comment that this would be vastly easier to read if the number were aligned and all had the same number of decimal places in a single column, good stuff. For sequential i/o the winners and losers are clear, and you can set cost and performance to pick the winners. Seems obvious that raid-1 is the loser for single threaded load, I suspect that it would be poor against other levels in multithread loads, but not so much for read.

--
Bill Davidsen <davidsen@xxxxxxx>
"Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark


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