Re: [Xen-users] Re: Xen Disk I/O performance vs native performance:Xen I/O is definitely super super super slow

[Joris Dobbelsteen <joris@xxxxxxxxxxxxxxxxxxxxx>]

Fajar A. Nugraha wrote, On 14-02-09 06:22:
> 2009/2/13 DOGUET Emmanuel <Emmanuel.DOGUET@xxxxxxxx>:
> > I have mount domU partition on dom0 for testing and it's OK.
> > But same partiton on domU side is slow.
> >
> > Strange.
> Strange indeed. At least that ruled-out hardware problems :)
> Could try with a "simple" domU?
> - 1 vcpu
> - 512 M memory
> - only one vbd
>
> this should isolate whether or not the problem is on your particular
> domU (e.g. some config parameter actually make domU slower).
>
> Your config file should have only few lines, like this
>
> memory = "512"
> vcpus=1
> disk = ['phy:/dev/rootvg/bdd-root,xvda1,w' ]
> vif = [ "mac=00:22:64:A1:56:BF,bridge=xenbr0" ]
> vfb =['type=vnc']
> bootloader="/usr/bin/pygrub"
I has one read somewhere that it could be caused by an interaction 
between LVM and Software RAID. You should break up your test into 
smaller fractions:
* Plain disk (NO RAID OR LVM)
* RAID only
* LVM only
* RAID + LVM

Maybe this isolates the issue a bit. I'm also strugling with similar 
numbers for disk performance, but since I run all my network services on 
top of one Xen box (personal system, not business) I have little 
intention to actually change it now. Its running an outdated Gentoo 
installation (upgrade attempts broke Xen in my case).
My memory might have failed after a year, but I believed that without 
RAID or LVM the performance was equal in both Dom0 and DomU.
- Joris

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