Re: [Qemu-devel] question about performance of dataplane

[Zhangleiqiang]

> -----Original Message-----
> From: Stefan Hajnoczi [mailto:address@hidden
> Sent: Monday, April 08, 2013 7:09 PM
> 
> On Sun, Apr 07, 2013 at 09:05:47AM -0500, Anthony Liguori wrote:
> > Zhangleiqiang <address@hidden> writes:
> >
> > > 1. Environment:
> > >   a). Qemu 1.4 master branch
> > >   b). kernel:  3.5.0-2.fc17.x86_64
> > >          c). virtual disks location:  the same local SATA harddisk
> > >   with ext4 fs
> >
> > I doubt you'll see any performance difference with a single SATA drive.
> > There's no real parallelism possible as you have exactly one spindle
> > available.
> 
> Sorry for the delay, catching up on emails after my Easter vacation.
> 
> I agree with Anthony here.  It seems your benchmark configuration is
> bottlenecked below the point where data plane makes a difference.
> 

I'm not understand what the "no real parallelism possible as you have exactly 
one spindle" means. Dose it means I should put os vdisk onto a different 
harddisk from the data vdisks? Or it means I should put data vdisk on different 
harddisks?  

But under the benchmark scenario mentioned above, even the os vdisk and data 
vdisks was on the same harddisk, the IOMeter only generated IO to data vdisks; 
Besides, the benchmark of dataplane disk and non-dataplane disk was did 
continuously other than simultaneously.

I have finished some benchmarks these days, and the results have already been 
sent to the mail list. It seems the dataplane has advantage when there is IO 
competition. I guess maybe the non-dataplane already reached the physical 
disk's IOPS upper limit in the scenario above so that data plane didn't make a 
difference? 

----------
Leiqzhang

Best Regards