Reclaiming Drives to Build a New RAID

07 January 2018

A couple years ago, I replaced my old spinner drives with matching SSDs. I left the old drives mounted but disconnected the cables. I’ve been watching my photo collection grow and consume about half my live storage, so I figured it was time to bring those slower spinning drives back online, so I can move my archive of old photos off my fast drives and get a little extra room.

I plugged in the first drive, and observed that it fortunately did not try to join the existing RAID arrays. lsblk showed me a list of drives and partitions and how they were currently used, so I could confidently cfdisk /dev/sda to wipe and recreate 1 primary partition on the drive as type fd (Linux raid autodetect). I rebooted to see the new partition table, and then installed and did the second drive (/dev/sdb in my case).

I setup the new drives in a mirror:

# create a new RAID1 mirror out of those new partitions:
mdadm --create /dev/md2 --level 1 --raid-devices=2 /dev/sda1 /dev/sdb1

# to ensure it's still called md2, and not md127 on reboot
update-initramfs -u

# create a filesystem
mkfs -t ext4 /dev/md2

# mount it to copy
mkdir /mnt/new
mount /dev/md2 /mnt/new

# migrate all my photos
rsync -av /home/john/Photos/ /mnt/new

After the initial migration, I tested it:

  • Rebooted

  • Checked that the array is there with the same name: cat /proc/mdstat (It initially had not kept the name, and that’s when I learned to update-initramfs above.)

  • Mounted the new array as /home/john/Photos,

  • Checked that Digikam still works.

That looked good, so it’s time to make it permanent:

  • Unmounted the new filesystem

  • Deleted all the old contents of /home/john/Photos

  • Added the new array to the /etc/fstab to mount it automatically

  • Rebooted!

Filed Under: Linux Computers