[pve-devel] default I/O scheduler - CFQ or Deadline?

[Eric Blevins]

On 05/07/2013 01:49 AM, Alexandre DERUMIER wrote:
> Sure !
> 3000 fsync with which hardware?  hardware raid with write cache ?
>
> For me it's always use deadline with shared storage and local hardware raid with cache.
>
> Don't need really cfq for reordering the ios, if the cache of the raid card or shared storage can handle this.	
This is a very good point.
CFQ might be better where the hardware is not good at ordering the writes.
I have always used deadline because all of my machines have 4GB BBU RAID
cards.

Maybe it would be best to make this option easily configurable vs simply
changing it.

>
>
>
> ----- Mail original ----- 
>
> De: "Dietmar Maurer" <dietmar at proxmox.com> 
> À: "Alexandre DERUMIER" <aderumier at odiso.com>, "Martin Maurer" <martin at proxmox.com> 
> Cc: pve-devel at pve.proxmox.com 
> Envoyé: Mardi 7 Mai 2013 05:48:47 
> Objet: RE: [pve-devel] default I/O scheduler - CFQ or Deadline? 
>
>> If I remember, some openvz features works only with cfq ? (ionice, openvz IO 
>> priorities) 
>> see: 
>> http://pve.proxmox.com/pipermail/pve-devel/2012-March/002488.html 
> Yes, but we measure incredible bad performance with cfq. We get fsync 
> rates of 250 instead of 3000 on ext4 (factor 12!). So iopriorities makes no 
> sense if you are already 10 time slower? 
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