Re: [libvirt] [PATCH] qemu: Adjust size for qcow2/qed if not on sector boundary

On 04/08/2014 10:26 AM, John Ferlan wrote: qed may require aligned multiples for size, but I thought that qcow2 can support an unaligned size (uncommon, but not technically impossible) - after all, the 'size' field in the qcow2 header (bytes 24-31) is an 8-byte value in bytes, not a count of sectors. Maybe we should try the user's size, and only then fall back to a rounded up alignment if the unaligned size fails. Hmm, now that I've experimented a bit: $ qemu-img create -f qcow2 img 12345 Formatting 'img', fmt=qcow2 size=12345 encryption=off cluster_size=65536 lazy_refcounts=off $ qemu-img info img image: img file format: qcow2 virtual size: 12K (12288 bytes) disk size: 196K cluster_size: 65536 Format specific information: compat: 1.1 lazy refcounts: false Wait a second - qemu-img rounded DOWN. That's wrong - it allocated less bytes than I requested. I think we need to first figure out what's going on with the qemu side, on whether qemu should be supporting unaligned requestes, before trying to paper around it in libvirt. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org