Re: [Xen-devel] Remus and Kemari...

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jan 21, 2010 at 08:12:21AM -0200, Gilberto Nunes wrote:
> Em Quarta-feira 20 Janeiro 2010, às 22:20:17, Brendan Cully escreveu:
> 
> Hi Brendan...
> 
> 
> > On Thursday, 14 January 2010 at 09:52, gilberto nunes wrote:
> > > I installed the Remus but had some problems.
> > > He leaves the VM very slow. I'm using a partition with DRBD / LVM.
> > > May even be that you say that has many layers (DRBD / LVM) that can
> > > influence on performance.
> > > But the interesting thing is that when Remus is not running the VM is
> > > light even with 512M of memory. And look what I'm talking about a Windows
> > > 2003 Standard Edition.
> > > The Remus to stop working inexplicably (at least for me)
> > > and let the VM's started in a state of the two nodes ...
> > 
> 
> > It's taken me a while to get Xen unstable running again, but now that
> > I have I can't reproduce any of these problems with an XP guest. It
> > remains responsive while Remus is running, and doesn't fail over
> > unless I kill it.
> 
> Right
> 
> > 
> > Disk access isn't likely to make a huge performance difference
> > (although I should say, simply parking a Remus VM on top of DRBD is
> > not safe, since there is no way of rolling back changes that have been
> > written since the most recent checkpoint). 
> 
> What you suggest... NFS!
> 
> > It sounds like your network
> > link between the primary and backup is either low capacity or flaky in
> > some way, or you have a loaded dom0.
> 
> My network between primary and backup server is a dedicate network, make with 
> a dedicate fast ethernet switch...
>

Not sure if Fast Ethernet is enough for Remus syncing? 
 
> I do not understand wath you say about that "I have a loaded dom0". On fact, 
> Xen always have a loaded dom0, right!
> 

I bet he meant "do you have high load on dom0", aka do you have high cpu usage 
in dom0? 
Try running "xm top" to figure out. And also normal "top" in dom0.

> > 
> > I'd recommend using single-processor dom0 and guest to start with, and
> > pinning the VCPUs to their own separate physical cores. 
> 
> I see. But how I do this!! I am a newbie. If you can point some ways to me, 
> I'll appreciate...
> 

See:
http://wiki.xensource.com/xenwiki/XenCommonProblems

There's a chapter called "How can I limit the number of vcpus my dom0 has?"
and "Can I dedicate a cpu core (or cores) only for dom0?"

-- Pasi



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