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

Stanislav German-Evtushenko ginermail at gmail.com
Mon Apr 13 11:48:19 CEST 2015

Hi Alexandre,

I've noticed your message in pve-devel (
http://pve.proxmox.com/pipermail/pve-devel/2015-April/014811.html) and
already tested aio=threads with cache=none - same result, it produced a lot
of out of sync blocks.

Best regards,

On Mon, Apr 13, 2015 at 12:16 PM, Alexandre DERUMIER <aderumier at odiso.com>

> Hi,
> Another difference is that cache=none|directsync is that vm use aio=native
> instead aio=threads.
> (you can try cache=none,aio=threads in you disk config to change the
> behaviour).
> Maybe it doesn't work well with drbd.
> ----- Mail original -----
> De: "Stanislav German-Evtushenko" <ginermail at gmail.com>
> À: "dietmar" <dietmar at proxmox.com>
> Cc: "pve-devel" <pve-devel at pve.proxmox.com>, "aderumier" <
> aderumier at odiso.com>
> Envoyé: Lundi 13 Avril 2015 10:23:19
> Objet: Re: [pve-devel] Default cache mode for VM hard drives
> Hello,
> I have an update on this issue.
> I have found circumstances when we get out of sync with directsync mode
> and made more test. What I found out so far was that out of sync only
> appear for cache modes with O_DIRECT, i.e. for those cache modes when host
> cache is bypassed. Write-back and write-through modes do not produce out of
> sync blocks with DRBD while "none" and "directsync" do.
> Best regards,
> Stanislav
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