Mirror system disk

Installation
1

If i choose 2 disks during installation the system will not boot and errors that sda2 is not btrfs when it was partitioned that way by installer.

If i install on one disk i cannot see a way to then mirror afterwards as you cannot grow the system pool by 1 disk and change raid level

any pointers?

cheers
Simon

2

Hi, you can mirror the system disk after installation by adding a second disk to its pool. The steps are as follows (assuming the second disk is /dev/sdb):

btrfs device add /dev/sdb /
btrfs fi balance start -dconvert=raid1 -mconvert=raid1 /
dracut -f

The last step updates the initrd so that your system would boot after this.

1 Like
3

Thanks @haoto. Have you experimented with making the /boot partition also into BTRFS?

4

I haven’t yet; will probably try if/when one of my USB sticks fails :smile:

5

I’d assume it would need to be able to read the initramFS as the default .config seems to build BTRFS support as a module.

That said there is a lot I don’t know about the linux kernel/boot process, I know enough to get the kernel source to compile and I know some of the safer options to remove during the config process (e.g audio support is largely useless on a server) but there’s a lot in there I leave well alone as I don’t know it’s importance.