On Sun, Aug 26, 2012 at 09:36:47AM +0100, Paul Maunders wrote: > root@proliantml110:/var/lib/libvirt/images# virt-sparsify > test-centos6-gpt.img.original test-centos6-gpt.img.sparsified > Create overlay file to protect source disk ... > Examine source disk ... > Fill free space in /dev/vda1 with zero ... > Copy to destination and make sparse ... > > Sparsify operation completed with no errors. Before deleting the old > disk, carefully check that the target disk boots and works correctly. > > After ... > > root@proliantml110:/var/lib/libvirt/images# du -h > test-centos6-gpt.img.sparsified > 882M test-centos6-gpt.img.sparsified > > root@proliantml110:/var/lib/libvirt/images# qemu-img info > test-centos6-gpt.img.sparsified > image: test-centos6-gpt.img.sparsified > file format: qcow2 > virtual size: 10G (10737418240 bytes) > disk size: 882M > cluster_size: 65536 > > The benefits remained when compressing the sparsified image too... > > root@proliantml110:/var/lib/libvirt/images# du -h > test-centos6-gpt.img.sparsified-compressed > 289M test-centos6-gpt.img.sparsified-compressed > root@proliantml110:/var/lib/libvirt/images# du -h > test-centos6-gpt.img.original-compressed > 369M test-centos6-gpt.img.original-compressed > > So thanks for the tip! > > I'm also going to experiment with backing images to build a base > library of gold images. A couple of points: (1) Since libguestfs 1.15.6, virt-sparsify has supported a --compress option. If you use '--convert qcow2 --compress' then this generates a compressed qcow2 file directly. (2) I don't use this option for my guest library. Instead I use raw sparse output and then 'xz --best' to compress the final image. Of course such an image isn't directly runnable, however xz does produce extremely small images, at the cost of taking a very long time to compress them. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://et.redhat.com/~rjones/virt-df/
