Rearranging an encrypted (LUKS) BTRFS spanning two disks

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1

I have a machine with two hard disks - a 500 GB NVME and a 1 TB hybrid drive (an HDD with a small SDD upfront for speeding up the most commonly-accessed items)
I installed Fedora using both disks and encrypted and the 1 TB disk contains /dev/sda1 fat32 /boot/efi, /dev/sda2 ext4 /boot, and /dev/sda3 [encrypted] BTRFS /, /home, and sd3 spans onto the NVME

Now I only have <300 GB total on my system, so I would really be using the NVME and not the HDD - is there a way to move things in-situ (and relatively painlessly) using the magic of BTRFS / Fedora? Or am I better off using my wondrous backups to wipe out the machine and do a clean reinstall?

2

I only have experience with non-encrypted disks.

  1. Remove device from btrfs
    Using Btrfs with Multiple Devices - btrfs Wiki

    Removing devices

    btrfs device delete is used to remove devices online. It redistributes any extents in use on the device being removed to the other devices in the filesystem. Example:

  2. copy efi and boot from existing boot disk to new bootdisk by dd

  3. create new btrfs filesystem on the remaining space of the new disk

  4. user btrfs send | btrfs receive to send over all btrfs subvolumes from old to new disk

  5. Modify boot entries / fstab to point to the new disk

  6. Disconnect old disk, and test boot with new disk.

3

Can you post the output from

fdisk -l /dev/sda
fdisk- l /dev/nvme0n1
btrfs fi us /               ##same as btrfs filesystem usage

It is possible to remove a device from a Btrfs pool, but there might be pre and post steps required, depending on the layout.

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4

I would backup and reinstall considering a different layout.
What you may want is /, /boot, and /boot/efion the NVME drive. That will give you a fast system.

Then, you can place /home onto the slower HDD and you get a lot of space there. And, if you are lucky, the ssd cache of your hybrid drive caches the frequently accessed files from you home directory.

Don’t span any volume over two drives! (if one drive fails your entire volume is broken).

5

Thanks - that fits with my thoughts
I have a 500 GB SSD available for the second slot - plan is backup, pull the HDD, reinstall on the 500 GB NVME alone and then have the SSD available to add if more store is required

If I have anything interesting other than “great success” to report, I’ll update the thread

1 Like
6

Thanks for all the replies.
Given that I have everything really well backed-up and didn’t want to do too much experimenting this time, I just nuked it and started over.
I took advantage of the carnage to switch from vanilla GNOME to KDE Scientific.
Everything seems fine - all the locally-backed up file copied over and my setting seem to be as they should; it’s just dropbox that is taking it’s sweet time reindexing