Red Hat Bugzilla – Bug 837941
Data loss when writing to qcow2-format disk files
Last modified: 2013-07-18 12:03:51 EDT
+++ This bug was initially created as a clone of Bug #836710 +++
For a full description of the bug, read this:
I tried your script and do more than 500 runs, it has no error output.
Is there need other steps to repoduce?
(In reply to bfan from comment #2)
> I tried your script and do more than 500 runs, it has no error output.
> Is there need other steps to repoduce?
This was actually a bug in qemu. The problem was that
qemu's qcow2 code used to crash, and libguestfs didn't
detect the crash (so instead you would just get occasional
lost data writes). Since then:
- qemu was fixed so the qcow2 code no longer crashes
- the kernel was fixed so it issues a write barrier for sync
- libguestfs has been modified to add a guestfs_shutdown
call to detect these crashes and report the error
instead of ignoring it.
Since this was all fixed a long time ago, it's unlikely
that you will be able to reproduce the bug. You would
have to go back to some quite old versions of qemu, kernel
My suggestion is that we close this bug. Even if the
qemu bug reappears, libguestfs will now detect and report
I am closing this, based on my previous comment.