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

Dietmar Maurer dietmar at proxmox.com
Thu May 28 14:04:10 CEST 2015

> > 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.

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