Which version of QEMU did you use? I think your report is a duplicate of bug report #919242. It was fixed by this commit:
commit 641543b76b82a8b361482b727e08de0c8ec093b0 Author: Stefan Weil <s...@weilnetz.de> Date: Sat Jan 21 13:54:24 2012 +0100 block/vdi: Zero unused parts when allocating a new block (fix #919242) Latest QEMU does not show an error with your test sequence. Regards, Stefan Weil ** Changed in: qemu Assignee: (unassigned) => Stefan Weil (ubuntu-weilnetz) -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/984953 Title: qemu-img alters (breaks) disk image content when converting to VDI Status in QEMU: New Bug description: When using "qemu-img convert" to create a VDI image, the VDI image is valid, but may contain an altered disk image. When such an image is run under VirtualBox, subtle bugs such as spontaneous segmentation faults happen because of broken system libraries. The following set of commands reproduces the bug (using the provided test disk image slice): bunzip2 < test-2M-2.raw.bz2 > test.raw qemu-img convert -O vdi test.raw test-2.vdi qemu-img convert -O raw test-2.vdi test-2.raw diff -qs test.raw test-2.raw # Output: Files test.raw and test-2.raw differ If the VDI image is created via "VBoxManage convertfromraw", everything is okay: VBoxManage convertfromraw test.raw test-3.vdi --format VDI qemu-img convert -O raw test-3.vdi test-3.raw diff -qs test.raw test-3.raw # Output: Files test.raw and test-3.raw are identical To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/984953/+subscriptions