sata hotswap pico-HOWTO

I had been unpleasantly informed by mdadm that sdc has been failing. Yey, another one – I thought. Not wanting to disrupt most of my day, I decided to try hot swapping the disk.

WARNING: this will potentially eat your data, and cause you to fall pray to the Nigerian email scam. Proceed with caution.

Before starting, I removed the bad disk from my raid1 (mirror) volume:

mdadm --del /dev/md0 /dev/sdc1

I learned on the interweb about the scsiadd utility and installed it:

apt-get install scsiadd

I then had to discover what sdc was on my system. Fortunately /sys had that information:

ls /sys/bus/scsi/devices/*\:0\:0\:0/block:* -d    

After discovering that 2:0:0:0 was really the same as sdc on my system, I took the drive off line:

scsiadd -r 2 0 0 0

I then swapped the disk for a new one, and added it back in:

scsiadd -a 2 0 0 0

NOTE: at this point I got a sdf, not a sdc as I would expect.

Next came the boring steps of fdisking the new disk, and running

mdadm --add /dev/md0 /dev/sdf1

… to add it back to the array.

LVM #

If you’re using LVM, you may want to look at pvmove which lets you migrate data from one PV to another. I have not tested this, but it could/should look like this:

pvcreate /dev/sde9
pvextend vg1 /dev/sde9
pvmove /dev/sdc9 /dev/sde9
pvreduce vg1 /dev/sdc9
pvremove /dev/sdc9

… given that your bad disk is sdc9 and your good one is sde9.