On Tue, Nov 08, 2016 at 03:05:24PM +0100, Kevin Wolf wrote: > [ Cc: qemu-block ] > > Am 08.11.2016 um 11:58 hat Richard W.M. Jones geschrieben: > > When using 'qemu-img create', if the file being created already > > exists, then qemu-img tries to read it first. This has some > > unexpected effects: > > > > > > $ rm test.qcow2 > > $ qemu-img create -f qcow2 -o compat=1.1,preallocation=off test.qcow2 1G > > Formatting 'test.qcow2', fmt=qcow2 size=1073741824 compat=1.1 > > encryption=off cluster_size=65536 preallocation=off lazy_refcounts=off > > refcount_bits=16 > > $ du -sh test.qcow2 > > 196K test.qcow2 > > > > > > $ rm test.qcow2 > > $ qemu-img create -f qcow2 -o compat=1.1,preallocation=falloc test.qcow2 1G > > Formatting 'test.qcow2', fmt=qcow2 size=1073741824 compat=1.1 > > encryption=off cluster_size=65536 preallocation=falloc lazy_refcounts=off > > refcount_bits=16 > > $ qemu-img create -f qcow2 -o compat=1.1,preallocation=off test.qcow2 1G > > Formatting 'test.qcow2', fmt=qcow2 size=1073741824 compat=1.1 > > encryption=off cluster_size=65536 preallocation=off lazy_refcounts=off > > refcount_bits=16 > > $ du -sh test.qcow2 > > 256K test.qcow2 # would expect this to be the same as above > > For me it's actually even more: > > $ du -h /tmp/test.qcow2 > 448K /tmp/test.qcow2 > > However... > > $ ls -lh /tmp/test.qcow2 > -rw-r--r--. 1 kwolf kwolf 193K 8. Nov 15:00 /tmp/test.qcow2 > > So qemu-img can't be at fault, the file has the same size as always. > > Are you using XFS? In my case I would have guessed that it's probably > some preallocation thing that XFS does internally. We've seen this > before that 'du' shows (sometimes by far) larger values than the file > size on XFS. That space is reclaimed later, though.
Yes I am, and indeed this looks like a filesystem artifact and not a problem with qemu-img. Thanks, Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org