Re: [Qemu-devel] [PATCH 0/3] Live migration without shared storage

[Liran Schour]

address@hidden (Lennart Sorensen) wrote on 08/09/2009
16:26:31:

> On Mon, Sep 07, 2009 at 06:40:51PM +0200, Pierre Riteau wrote:
> > I'm trying blk migration (not incremental) between two machines
> > connected over Gigabit ethernet.
> > The transfer is quite slow (about 2 MB/s over the wire).
> > While the load on the sending end is low (vmstat says ~2000 blocks in/
> > sec, and top says ~1% in io wait), on the receiving end I see almost
40%
> > CPU in io wait, kjournald takes 20% of the CPU and vmstat reports
~14000
> > blocks out/sec.
> >
> > Hosts are running Debian Lenny (2.6.26 32 bits), kvm-87 + your patches.
> > The guest is also running Debian Lenny and is idle io wise. I tried
with
> > both idle and full cpu utilization, it doesn't change anything.
>
> If you happen to be using ext3, then that might explain it.  ext3 has
> long had issues with performance while slowly writing a large file
> (this affects mythtv a lot for example).  2.6.30 should improve things a
> lot, although ext3 will never be great.  ext4 is better, and hopefully
> btrfs will be great (when done).  xfs is also supposed to handle such
> tasks very well.
>
> --
> Len Sorensen

I found performance issues in the patch itself. I will first submit a new
patch
and maybe then will be able to talk about the fs performance.

Thanks,
- Liran