[ovirt-devel] Disk sizes not updated on unmap/discard

Hi, currently, when we run virt-sparsify on VM or user runs VM with discard enabled and when the disk is on block storage in qcow, the results are not reflected in oVirt. The blocks get discarded, storage can reuse them and reports correct allocation statistics, but oVirt does not. In oVirt one can still see the original allocation for disk and storage domain as it was before blocks were discarded. This is super-confusing to the users because when they check after running virt-sparsify and see the same values they think sparsification is not working. Which is not true. It all seems to be because of our LVM layout that we have on storage domain. The feature page for discard [1] suggests it could be solved by running lvreduce. But this does not seem to be true. When blocks are discarded the QCOW does not necessarily change its apparent size, the blocks don't have to be removed from the end of the disk. So running lvreduce is likely to remove valuable data. At the moment I don't see how we could achieve the correct values. If anyone has any idea feel free to entertain me. The only option seems to be to switch to LVM thin pools. Do we have any plans on doing that? Tomas [1] https://www.ovirt.org/develop/release-management/features/storage/pass-di... -- Tomáš Golembiovský <tgolembi(a)redhat.com&gt;