Ceph » rbd

When trying to use the cache=writeback i found out that this doesn't change anything.

Sage suggested that something might has to be implemented in the rbd driver.

Searching trough the qcow2 code confirms that:

rbd uses bdrv_file_open which does not support Writeback caching, where qcow2 uses bdrv_open, which does support wb.

Although using writeback could lead to data loss in case of a crash or power failure, it might be usefull in certain situations.