[pve-devel] new cache benchmark results

[Alexandre DERUMIER]

>>Has anybody tested whether creating the filesystem with various block 
>>sizes circumvent this bug? 

Hi, I'm not sure the problem come from the filesystem block size.

I think if more about sectors alignement betwwen physical drive (4K) and virtual drive (qemu default is 512bytes)

some interresting patch
http://comments.gmane.org/gmane.comp.emulators.qemu/126267
" block: add support for 4k logical blocks"
" 1. This patch aims to add 4k logical support for qemu running on a host
> with 4k logical block size, right?

No, it adds support for 512b logical block sizes running on a host with 
4k logical block size and cache=none.  This is suboptimal as it requires 
bounce buffers, but it can happen with migration and until libvirt 
provides a knob for the guest's logical block size.

> For guest, we can use
> logical_block_size=4096 to achieve that even on a host with the
> logical_block_size of 512. Am I right?
"

So this patch seem to get default qemu drive of 512b working on 4K drive. (but suboptimal).

To be perfect, we need to pass logical_block_size=4096 to qemu command line

qemu  -device virtio-blk-pci,logical_block_size=4096,physical_block_size=4096,....


But user on forum seem to say that it wasn't working :(


----- Mail original ----- 

De: "Michael Rasmussen" <mir at datanom.net> 
À: pve-devel at pve.proxmox.com 
Envoyé: Jeudi 8 Novembre 2012 18:40:17 
Objet: Re: [pve-devel] new cache benchmark results 

On Thu, 08 Nov 2012 18:06:47 +0100 (CET) 
Alexandre DERUMIER <aderumier at odiso.com> wrote: 

> Yes, I remember the post in the forum. It doesn't work with cache=none or cache=writeback 
> 
Has anybody tested whether creating the filesystem with various block 
sizes circumvent this bug? 

-- 
Hilsen/Regards 
Michael Rasmussen 

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