Upgrade to 18TB raw, 12TB usable

• Retired remaining 2TB disk
• Added two 3TB disks.

Add 3TB disk and grow md6

mdadm --add /dev/md6 /dev/sdh # replaces failed disk
# resync
mdadm --add-spare /dev/md6 /dev/sdb  # previously a backup disk
mdadm --add-spare /dev/md6 /dev/sdg
# fail old 2TB disk
mdadm --fail /dev/md6 /dev/sda
mdadm --remove /dev/md6 /dev/sda
# resync and grow across all 3TB disks
mdadm --grow /dev/md6 --raid-devices=6  # will this pick up the new device size?

Extend LUKS

cryptsetup resize /dev/mapper/crypt-md6

Extend Logical Volumes

pvresize /dev/mapper/crypt-md6
lvextend -L +1T /dev/vg-md6/media
resize2fs /dev/vg-md6/media &
lvextend -L +300G /dev/vg-md6/home
resize2fs /dev/vg-md6/home &