Mdadm

raid chunk size set to 64k

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

1. yum install kmod-xfs xfsdump xfsprogs

1. mkfs.ext3 -m 0 -b 4096 -E stride=16 /dev/mapper/sil_ajaeadddahbg
2. bonnie++ -d /mnt/raid5/tmp -u drew -f

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

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

1. This step must come first.
2. 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

1. if you use more than the default 64kb stripe with raid5
2. this feature is broken so you need to limit it to 30MB/s
3. 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

1. 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