[pve-devel] [PATCH qemu-server] add discard_granularity to 4M for rbd storage

[Alexandre DERUMIER]

>>IMHO: I would be up for this approach, as a first measure, so the discard 
>>granularity can be overwritten.

I'll rework my patch on qemu-server and make a new sub in pve-storage plugins to retrieve the block size.


>> A second step may be that Qemu should be able to work with the proper granularity by itself. 

I really don't known if qemu is able to retrieve the value from zfs (as it's a simple block storage).
I think the value is the cluster block size, it's possible to retreive it from rbd, qcow2,... when we have a specific block driver.

----- Mail original -----
De: "Alwin Antreich" <a.antreich at proxmox.com>
À: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Vendredi 29 Juin 2018 10:17:56
Objet: Re: [pve-devel] [PATCH qemu-server] add discard_granularity to 4M for rbd storage

On Fri, Jun 29, 2018 at 08:12:13AM +0200, Alexandre DERUMIER wrote: 
> and for zfs , we can retrieve block size with: 
> 
> zfs get volblocksize rpool/data/vm-105-disk-1 
> NAME PROPERTY VALUE SOURCE 
> rpool/data/vm-105-disk-1 volblocksize 8K default 
> 
> 
> 
> Maybe can we change current discard option to: 
> 
> discard : 0 : disable 
> 1 : enable (with defaut qemu value) 
> 2 : enable : auto best value (zfs/rbd autodect and qemu for others storage) 
> 1024-... : custom user value 
> 
> ? 
IMHO: I would be up for this approach, as a first measure, so the discard 
granularity can be overwritten. A second step may be that Qemu should be 
able to work with the proper granularity by itself. 

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