Multi-device btrfs support about disko HOT 6 CLOSED

cc @lilyinstarlight

from disko.

What type of backing devices? I've not used multidevice btrfs before but I thought you only needed the one mkfs command without anything special before it

from disko.

Yes, to make a multidevice btrfs filesystem, you use a command like follows:

mkfs.btrfs -m raid1 -d raid1 /dev/device1 /dev/device2

Looking at the source of this module, I can make that happen by configuring device1 and adding "-m dup -d dup /dev/device2" as extra mkfs options.

However, before the mkfs.btrfs is run, the devices have to be ready. I use LVM on LUKs on all my disks and use a lv on each disk as the devices for the btrfs volume. Thus the btrfs filesystem depends on both disk's logical volumes. Adding that dependency is what I could not figure out

from disko.

If it helps, my current disk setup is here: https://github.com/accelbread/config-flake/tree/master/nixos/common/disks

from disko.

Yeah I was worried you were gonna say something like that

As disko is right now, it creates LVs in lexographical order, so as long as you put the type = "btrfs" content in the last lv alphabetically, they should all be created by that point and it will technically work to provision. I think you only need to mount one device for btrfs to get all of them, so it should even work with the NixOS config part too like that

As it is right now though, I don't think there is an explicit way to order devices by dependency (#80 is related) and there is definitely no expicit multi-device btrfs support (that would probably have to be its own top-level type like VGs are now, but given mounting only needs to happen for one device anyway, the extraArgs kludge is probably sufficient)

from disko.

Thanks; that answers my question, so I'll close the issue.

from disko.