[pve-devel] vm migration + storage migration with ndb workflow notes

[Alexandre DERUMIER]

>>So I guess they are already aware of that problem. 
Yes, Paolo have also reply me.


"> Any idea why drive-mirror is so slow ? (maybe does it use directsync when mirroring ?)

No, it doesn't.  Probably it's because the image is sparse?  The current
code in git master has a very coarse granularity (1 MB).

Please try the blkmirror-job-1.4 branch from my github repo
(git://github.com/bonzini/qemu.git).  That branch uses the qcow2 file's
cluster size as the granularity, and has other optimizations that kick
in when the image is sparse.
"

I think it's related to sparse file. 
Because my 32GB file have only around 2GB datas, and qemu-img seem to skip them and but not drive-mirror.



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

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Lundi 21 Janvier 2013 12:29:15 
Objet: RE: [pve-devel] vm migration + storage migration with ndb workflow notes 

I just found a patch from last week on the qemu-devel list: 

[Qemu-devel] [PATCH v2 00/12] Drive mirroring performance improvements 

So I guess they are already aware of that problem. 

> >>This should be as fast as qemu-img. Please can you post your findings 
> >>on the pve-devel list - this looks like a serious bug to me. 
> I'll send a msg to the qemu mailing. 
> 
> Maybe with drive-mirror the target file is open in directsync ? 
> 
> ----- Mail original ----- 
> 
> De: "Dietmar Maurer" <dietmar at proxmox.com> 
> À: "Alexandre DERUMIER" <aderumier at odiso.com> 
> Cc: pve-devel at pve.proxmox.com 
> Envoyé: Lundi 21 Janvier 2013 10:18:20 
> Objet: RE: [pve-devel] vm migration + storage migration with ndb workflow 
> notes 
> 
> > I see a big speed difference 
> > 
> > for a 32gb file, migrate on same local, qcow2 -> raw, both writeback 
> > 
> > qemu-img : 30s 
> > drive-mirror (with paused vm) : 5min 
> 
> This should be as fast as qemu-img. Please can you post your findings 
> on the pve-devel list - this looks like a serious bug to me.