Error Mounting Docker/Linstor Volume after Pool Resize

LINSTOR
2

I think you should show the whole series of steps to reproduce the problem from scratch, including exactly what sort of storage pool you’ve set up (is it LVM?)

In principle, growing a storage pool, growing a volume, and using online resize2fs inside the volume when its size increases are all fine things to do (and I have done them successfully without problems, albeit using Proxmox not Docker). But resize2fs will not reduce the size of a volume while it is mounted.

Now, I see you’re getting an “Error response from [docker] daemon” at startup time. Is docker itself trying to resize the volume again at container start?

You should check the exact sizes of volumes e.g. with blockdev --getsize64 /dev/drbdXXXX

Note that the volume you get from Linstor may be slightly bigger than you asked for. For example, suppose you ask for 1GiB = 1024MiB. On LVM that’s 256 extents (4MiB). DRBD needs some space for metadata, so Linstor asks for the next size up, which is 1028MiB (257 extents). DRBD metadata goes at the end, but it doesn’t use the whole 4MiB, so you end up with a volume that’s slightly larger than 1GiB.

Usually that’s not a problem, unless you subsequently try to copy this onto a volume on some other system which is exactly 1GiB.

However, I can imagine the following scenario:

  1. You said you called “resize2fs” yourself inside the container. If you didn’t specify the size it will grown the filesystem to the full available size, which is slightly more than 1GiB
  2. Docker mounts the volume
  3. Docker itself calls “resize2fs” again at container startup, but explicitly specifying the size it originally requested (i.e. 1GiB)
  4. At this point, resize2fs barfs because Docker is asking it to do an online shrink of the volume

The way to fix this would be to run resize2fs when the volume is unmounted, giving the exact size required. resize2fs will then move stuff around to shrink the filesystem. Aside: you need to run e2fsck -f before resize2fs in this case, but resize2fs will refuse to run you if you haven’t.

And if this is the problem, the solution is not to call resize2fs yourself inside the container, but let docker do it.

Good luck!