On Tue, Apr 23, 2019 at 01:30:28PM +0200, Martin Kletzander wrote: > I am using qemu-img with nbdkit to transfer a disk image and the > update it with extra data from newer snapshots. The end image > cannot be transferred because the snapshots will be created later > than the first transfer and we want to save some time up front. You > might think of it as a continuous synchronisation.
It's important to note here that Martin is reading the data from a VMware server, so this is not something that can be solved with qemu's own snapshots. [...] I think the following is an even simpler demo which gets to the nub of the problem as I understand it: $ rm -f disk.img snap.img $ dd if=/dev/urandom of=disk.img bs=2M count=1 $ dd if=/dev/zero of=snap.img bs=2M count=1 $ qemu-img convert -n -p snap.img disk.img $ hexdump -C disk.img | head 00000000 18 30 e8 1f 09 f0 bb 2c 2f c7 b3 97 8f 12 fe 4b |.0.....,/......K| 00000010 66 f7 28 cb 8e 72 2a 37 6b fa 98 2e a0 e6 d9 cf |f.(..r*7k.......| [etc] <- ie. not zeroes Should we expect disk.img to contain zeroes at the end? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW
