I'm looking to add a new drive to an existing NAS server, and would appreciate a second look at my plan before I pull the trigger. Part of the challenge is the new disk will be added to an existing RAID, which itself is encrypted, and also makes up a physical-volume in an existing volume-group.
Current Setup:
There is a single logical-volume ('media') and volume-group ('raid') made up of two physical-volumes ('/dev/mapper/crypt1' and '/dev/mapper/crypt2'). Each physical-volume is a LUKS-encrypted RAID: a (1) RAID-5 made up of 4x4TB drives ('md0'), and a (2) RAID-1 made up of 2x8TB drives ('md127').
user@server:~$ lsblk
sdb 8:16 0 3.7T 0 disk
└─md0 9:0 0 10.9T 0 raid5
└─crypt1 253:0 0 10.9T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
sdc 8:32 0 3.7T 0 disk
└─md0 9:0 0 10.9T 0 raid5
└─crypt1 253:0 0 10.9T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
sdd 8:48 0 3.7T 0 disk
└─md0 9:0 0 10.9T 0 raid5
└─crypt1 253:0 0 10.9T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
sdf 8:80 0 3.7T 0 disk
└─md0 9:0 0 10.9T 0 raid5
└─crypt1 253:0 0 10.9T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
sdg 8:96 0 7.3T 0 disk
└─md127 9:127 0 7.3T 0 raid1
└─crypt2 253:1 0 7.3T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
sdh 8:112 0 7.3T 0 disk
└─md127 9:127 0 7.3T 0 raid1
└─crypt2 253:1 0 7.3T 0 crypt
└─raid-media 253:2 0 18.1T 0 lvm /media
Objective:
I would like to add a third 8TB disk to the 'md127' array without losing the existing data. And since this will grow the array from two drives to three, I would like to reshape the array from RAID-1 to RAID-5 for a net gain of approximately 8TB of free storage.
Step 0: Unmount the Logical Volume, and Convert RAID-1 to RAID-5
unmount /dev/raid/media
mdadm --grow /dev/md127 --level=5
Step 1: Add HDD to RAID-5
Supposing the new drive is added as '/dev/sda':
$ mdadm --add /dev/md127 /dev/sda
$ mdadm --grow --raid-devices=3 --backup-file=~/md127_grow.bak /dev/md127
I understand this can take a long time. One can check the progress with mdadm --detail /dev/md0.
Step 2: Enlarge the physical-drive, volume-group, and filesystem
pvresize /dev/mapper/crypt2
lvextend -l +100%FREE /dev/raid/media
resize2fs /dev/raid/media
I took my notes from this page and this page, neither of which consider any encryption. My plan above doesn't consider encryption, except when identifying the physical volume (e.g. '/dev/mapper/crypt2'). I'm guessing that's the only thing I do differently.
I would appreciate any thoughts or comments you may have. Many thanks for the help.
