Mdadm

1. yum install kmod-xfs xfsdump xfsprogs

Create md device

Create a raid5 device with 256 chunk size on 4 devices with out any hot spares.

# mdadm --create /dev/md0 --level=raid5 --chunk=256 --raid-devices=4 --spare-devices=0 /dev/sd[b-e]

Create filesystem

Create an ext3 file system with 0% space reserved for boot, a 4096 block size, and a raid stride of 16 ( 16 * 256 = 4096 | stride*chunk=block)

# mkfs.ext3 -m 0 -b 4096 -E stride=16 /dev/md0

Performance Testing

Bonnie++

# bonnie++ -d /mnt/raid5/tmp -u drew -f

Iozone

-a auto -b output_excel file -i run read test -i run write test

# iozone -a -b werd.xls -i 0 -i 1 -C -E

Additional Tunables=

# This step must come first.
# See: http://www.3ware.com/KB/article.aspx?id=11050

echo "Setting max_sectors_kb to chunk size of RAID5 arrays..."
for i in sdc sdd sde sdf sdg sdh sdi sdj sdk sdl
do
   echo "Setting /dev/$i to 128K..."
   echo 128 > /sys/block/"$i"/queue/max_sectors_kb
done

echo "Setting read-ahead to 64MB for /dev/md3"
blockdev --setra 65536 /dev/md3

echo "Setting stripe_cache_size to 16MB for /dev/md3"
echo 16384 > /sys/block/md3/md/stripe_cache_size

# if you use more than the default 64kb stripe with raid5
# this feature is broken so you need to limit it to 30MB/s
# neil has a patch, not sure when it will be merged.
echo "Setting minimum and maximum resync speed to 30MB/s..."
echo 30000 > /sys/block/md0/md/sync_speed_min
echo 30000 > /sys/block/md0/md/sync_speed_max
echo 30000 > /sys/block/md1/md/sync_speed_min
echo 30000 > /sys/block/md1/md/sync_speed_max
echo 30000 > /sys/block/md2/md/sync_speed_min
echo 30000 > /sys/block/md2/md/sync_speed_max
echo 30000 > /sys/block/md3/md/sync_speed_min
echo 30000 > /sys/block/md3/md/sync_speed_max

# Disable NCQ.
echo "Disabling NCQ..."
for i in sdc sdd sde sdf sdg sdh sdi sdj sdk sdl
do
   echo "Disabling NCQ on $i"
   echo 1 > /sys/block/"$i"/device/queue_depth
done