On Thu 16 Aug 2018 10:20:12 AM CEST, yang.bi...@zte.com.cn wrote:
>>If there is no backing file or snapshot you still need to fill the
>>cluster with zeroes, and that's going to be slower with larger
>>clusters.
>
> If not fill zeroes and only write guest data ,what`s wrong could
> happen
> > > > When use cluster_size=1M qcow2 newly created to test "32k rand
> > > > write" in the VM,We get low performance within VM。But there
> > > > are huge “write” requests in HOST which falls into qemu
> > > > stack of"perform_cow".
> > > The reason why this happens is because clusters are the
