Re: domU NFS performance

["Karsten M. Self" <karsten@xensource.com>]

Nicholas Lee wrote:

>I've written up a short review of the past few months experimenting
>with a Xen based Ubuntu NX thin client server.
>
>http://stateless.geek.nz/2005/08/29/xen-disk-performance/
>
>I'm wondering if other people have experience similar stalling issues
>with  NFS services in a domU.  Is it a known issue?
>  
>
Nicholas:  I'm with Keir, this shouldn't be happening.  I'm with 
XenSource QA, this looks like an interesting situation.

Could you provide us with some additional information (some you've 
already given).

There's a script I've written to gather system information called, oddly 
enough, system-info.  Find a copy at 
http://linuxmafia.com/~karsten/Download/system-info (I'll see about 
getting this to the Cambridge site, we're looking at using this here).

Try running that on both the DomU and physical system as this will give 
us an idea of your system state as well.

You might also want to:

  - Provide specific NFS version info.
  - Check system logs on client and server for any possible related info.
  - Monitor traffic (tcpdump, ethereal, iptraf) to determine if latency 
is visible at network / protocol level.
  - Provide specific network hardware specs.  We *are* seeing issues 
with specific cards, and have seen some quirks with hub/switch 
configurations.

My own experience with mutt is that it can be notoriously laggy 
particularly dealing with large or frequently updated mailboxes.  It may 
not be the best general purpose network performance test tool.  Perhaps 
netperf (packaged for Debian) would be more useful.

As Kier indicates, we're largely dogfooding internally with services run 
via Xen DomUs, so this is a bit of a puzzler.

Cheers.

-- 
Karsten M. Self <karsten@xensource.com>
XenSource, Inc.
2300 Geng Road #250                                +1 650.798.5900 x259
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