[pve-devel] Default cache mode for VM hard drives

[Dietmar Maurer]

> > ceph use O_DIRECT+O_DYNC to write to the journal of osds.
> Is this done inside KVM process? If so then KVM keeps buffer for this
> O_DIRECT writing. Therefore if multiple threads can access (and change)
> this buffer at the same time then the similar issue can happen in theory.

It only happens if the underlying device is mdraid or drbd. A OSD is 
always a single device, so this would not be a problem.