[pve-devel] Fwd: Re: recommanded cache setting for rbd image

[Dietmar Maurer]

> >> But why does a guest do not support flushes? What kind of guest is that?
> 
> also here :https://patchwork.kernel.org/patch/1151041/
> 
> "VIRTIO_BLK_F_FLUSH has been introduced in Linux 2.6.32 (in 2009) and was
> backported to RHEL/CentOS 5.6 (in 2010).  The Windows drivers have two
> bugs, which I reported on the Red Hat Bugzilla as bugs 837321 and 837324.
> With these patches they will suffer a performance hit but gain correctness."
> 
> So it's mainly for virtio-blk with kernel < 2.6.32 and buggy windows virtio
> drivers.

Well, I would consider a block driver which does not support sync/flush 'very buggy'.