Recently upstream qemu and RHEL 6 have seen a lot of qcow2 fixes, most of which concern error handling. They fix bugs where errors are either completely ignored or (more often) where a wrong error code is propagated, e.g. always EIO regardless of what error really occurred. These bug fixes need to be backported to RHEL 5 as RHEV makes use of error paths even under normal conditions.
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: When using QCOW2 disk images, certain I/O operation or disk space depletion errors could potentially have caused image corruption or a virtual guest to stop running. This was due to the improper error-handling code for QCOW2 disk images. This has been fixed with this update so that the aforementioned types of errors are handled correctly, thus increasing QCOW2 disk integrity in such situations.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0028.html