On 04/12/2013 03:53 AM, Daniel P. Berrange wrote: > On Fri, Apr 12, 2013 at 05:25:23PM +0800, me,apporc wrote: >> After snapshot-delete, the qcow2 image file size doesn't decrease, isn't >> that a waste of disk space? > > Yes, but that's life. When deleting an internal qcow2 snapshot, > QEMU will just mark the clusters as unused, it won't return them > to the underlying filesystem. These unused clusters will, however, > be re-used if the qcow2 file needs to grow later. > >> Would someone please tell me how to decrease the file size when >> snapshot-delete, if that's possible? > > You can't do it in place. The only option would be to use qemu-img > to clone the qcow2 file to a new qcow2 file & delete the original. Check out 'virt-sparsify' from libguestfs-tools, which is designed to help you minimize disk space (including this trick of copying from one qcow2 to another to reduce space occupied by now-unused clusters). Meanwhile, if you are really ambitious, write a patch to upstream qemu that can do a defrag pass on an existing qcow2 image, and expose it through both qemu-img (for manipulating offline disks) and a QMP monitor command (so that we can request an online defrag without any noticeable guest downtime). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
Attachment:
signature.asc
Description: OpenPGP digital signature
_______________________________________________ libvirt-users mailing list libvirt-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvirt-users
