Re: [Qemu-devel] Re: Comparing New Image Formats: FVD vs. QED

[Chunqiang Tang]

> On Tue, Feb 15, 2011 at 7:45 PM, Chunqiang Tang <address@hidden> 
wrote:
> >> Chunqiang Tang/Watson/IBM wrote on 01/28/2011 05:13:27 PM:
> >> As you requested, I set up a wiki page for FVD at
> > http://wiki.qemu.org/Features/FVD
> >> . It includes a summary of FVD, a detailed specification of FVD, and 
a
> >> comparison of the design and performance of FVD and QED.
> >
> >> See the figure at http://wiki.qemu.org/Features/FVD/Compare . This
> > figure
> >> shows that the file creation throughput of NetApp's PostMark 
benchmark
> > under
> >> FVD is 74.9% to 215% higher than that under QED.
> 
> File creation on a sparse image is currently limited by the fact that
> the QED implementation serializes allocating writes.  In earlier QED
> patch series I had fine-grained metadata locking so allocating writes
> scale better but that lead a regression on another benchmark.  I have
> this on my todo list.
> 
> This is an implementation-specific limitation and is unrelated to the
> file format.  It doesn't tell us about a difference between formats.

I agree that a good comparison of the design difference is as important as 
the quantitative numbers. I previously posted the spec of FVD as well as a 
comparison of FVD and QED on wiki, http://wiki.qemu.org/Features/FVD . 
Part of the comparison was also copied in an early email of this thread. I 
welcome comments and feedback on the design aspect.