On Tue, Feb 15, 2011 at 7:45 PM, Chunqiang Tang <ct...@us.ibm.com> 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. Stefan
