Il 02/01/2014 17:15, Richard W.M. Jones ha scritto: > > My (possibly weak) understanding of the upstream qemu code is that > unmap/discard/trim is not supported in qcow2. It is only supported in > raw files when using a POSIX-like host OS which has either of: > > - block devices supporting BLKDISCARDZEROES > - files on XFS > - files on other filesystems that support FALLOC_FL_PUNCH_HOLE (eg ext4)
It doesn't have to support BLKDISCARDZEROES, only BLKDISCARD. I test it with scsi_debug using both lbprz=0 and lbprz=1 (which becomes BLKDISCARDZEROES unset and set respectively). Otherwise this is correct. > Having said that, I did some tests using libguestfs and I could not > show that unmap was working, either using raw or qcow2 (both on ext4), > with virtio-scsi, and recent kernel & qemu. I did not see any errors, > but also I don't see what I'm doing wrong. Can you share more? Paolo
