I am following along the process of adding a second drive to a BTRFS filesystem, this one effectively is /home. The device is using LUKS and the new drive is already given a LUKS partition of equal size. I am following resources such as under conversion section and used the commands sudo btrfs device add -f /dev/mapper/luks-blah-blah /home; sudo btrfs balance start -dconvert=raid1 -mconvert=raid1 /home. The only other thing I have done myself is add the crypttab entry for the new device and ensured the key slot is correct. What method is needed beyond these steps? I am wondering if there should be edits to the fstab also? the fstab is using the specific opened volume of the old device like /dev/mapper/luks-old-device but since the filesystem pool contains both devices they should both be usable. Specifically since I have the new device unlocked in crypttab I think there should be nothing else needed to allow the RAID1 to work but want to check first. Thank you!
I am not a LUKS user, but I am fairly certain it’s the same as without LUKS.
You can boot exactly the same way as before.
I would just manually add your second device as a another GRUB entry. You can boot either btrfs device. (Then the other is there in case of failure.)
I don’t know if it is proper to have two devices set to mount to the same place even if they are set to be one filesystem e.g. RAID1. It feels wrong, maybe I will leave fstab alone but there was a section of that same link here at the bottom explaining registration in fstab that doesn’t look like my fstab entries. should I change the line as it currently is? /dev/mapper/luks-old-device /home btrfs subvol=/@home,defaults,discard=async,ssd,noatime,compress=zstd:3 0 0
Btrfs is not like traditional file systems that can only be mounted once, you can mount it as many times as you want.
It’s actually how subvolumes work… You mount the same device with just a different subvol option.
When you have a btrfs mirror (RAID 1), the UUID is the same for both devices. So there shouldn’t be any changes, if you are using the proper UUID in there.
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