[pve-devel] cache unsafe write for qemu-img convert, vma extract and vmstate snapshot

[Eneko Lacunza]

El 01/08/16 a las 08:50, Alexandre Derumier escribió:
> As reported by  Eneko Lacunza,
> ceph/rbd by default use writethrough even if writeback is defined, until a flush is detected.
>
> We currently use writeback without sendind any flush for 3 things:
>
> qemu-img convert : (default is unsafe, but we force writeback in qemuserver)
> vma restore on target destination
> vmstate snapshot
>
> The patches serie  set unsafe opening (BDRV_O_NO_FLUSH).
>
> And also fix the rbd drive to disable cache_writethtrough_until_flush if cache=unsafe
>
> @Eneko Lacunza : Can you test it ? I have rewrote your last patch (http://pve.proxmox.com/pipermail/pve-devel/2016-July/022226.html),
>                  to handle vma extract and vmstate snapshot
I can confirm that extract performance is good with your patch series.

On a side note, it's interesting to see that either a series of patches 
or a slow almost-holiday week is needed to readers in the list pay 
attention ;)

Cheers
Eneko


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