Hello Openstack-Discuss,

after some digging I found out that cinder learned to resize attached (in-use) volumes quite a while ago with the introduction
of the initial "extend 'in-use' volume" feature:
https://review.opendev.org/c/openstack/cinder/+/454287/

The support was then extended to also cover Ceph RBD backed volumes with:
https://review.opendev.org/c/openstack/nova/+/613039/

Since this is only about the cinder part, I was wondering if nova would ever find out and would actively rescan the device / volume and quintessentially present an increased new size to the guest. Apparently this is where a certain volume-extended event comes into play: https://review.opendev.org/c/openstack/nova/+/454322/ that is to be emitted by cinder when a volume had been extened.

I then went head and tried this with the openstack cli (as Horizon does not seem to support / offer to resize in-use volumes.
I run Openstack Train with Ceph RBD as storage. First I ran into an issue with the openstack cli (https://bugs.launchpad.net/cinder/+bug/1871759/comments/2) but using

  cinder extend $volumeid $newsize

I was able to resize in-use volumes just fine.

The only thing missing was the propagation to the guest. I played around with SCSI rescans, but that did not work, reboots also failed to do anyting in this regards. Stopping and starting the VM did work, but why having the capability to online-resize an attached volume when not being able to resize the guest volume as well?

Apparently there seems to be an old and somewhat similar observation / bug with https://bugs.launchpad.net/nova/+bug/1369465

So I was simply wondering if this is expected to be working?
Are there any special settings / options I need to set to enable this feature?

Thanks and with kind regards

Christian