egork's Journal: RAID Array in Intrepid

If the RAID you have created does not start after the reboot, you might wish to add a line in the initramfs-tools/init file:

/usr/share/initramfs-tools/init

# to stop a race condition with md

157 maybe_break mount
158 sleep 5
159 log_begin_msg "Mounting root file system..."

sudo /usr/sbin/update-initramfs -uk all

# run to rebuild the image
Make sure if you add it it is to the "mount" line. The line numbers are likely different with your system. You might start with 10 instead of 5, seconds delay. Ubuntu Forum Discussion
known bug in Intrepid has no influence on the creation of the array.

to check the SMART status of the drives do this

for letter in a b c d e f; do echo "############## Below the information for the drive /dev/sd$letter ##########" && sudo smartctl -H -l error /dev/sd$letter ; done

add internal bitmap to reduce rebuild time

sudo mdadm --grow --bitmap=internal /dev/md0

better still add external bitmap to speed up the write speed to compared to internal bitmap

sudo mdadm --grow --bitmap=none /dev/md0 #remove bitmap sudo mdadm -G /dev/md0 -b /media/persistent_temp/md0_intent_var # my /var is mounted into ramdisk

add to /etc/rc.local to further optimize write speed further.

echo 8192 > /sys/block/md0/md/stripe_cache_size

check drive features

for letter in a b c d e ; do echo "Drive /dev/sd$letter" && sudo hdparm -i /dev/sd$letter ; done

Turn of APM and spin down. Set sound management to "fast". APM is not supported on my WD drives.

for letter in a b c d e ; do echo "Drive /dev/sd$letter" && sudo hdparm -B255 -S0 -M254 /dev/sd$letter ; done

Recover sequence

sudo mdadm --assemble --force /dev/md0 --uuid=YOUR_UUID /dev/sd{a,b,c,d,e}1
sudo mdadm --query --detail /dev/md0
sudo fsck.jfs -v /dev/md0
sudo mount /dev/md0
sudo watch cat /proc/mdstat
sudo mdadm /dev/md0 --add /dev/DEVICE_TO_ADD