RE: [Xen-users] NFS DomU Client Performance

Petersson, Mats
Wed, 23 Aug 2006 17:24:11 -0000

> -----Original Message-----
> From: HAWKER, Dan [mailto:dan.hawker@astrium.eads.net]
> Sent: 23 August 2006 17:45
> To: Petersson, Mats; xen-users@lists.xensource.com
> Subject: RE: [Xen-users] NFS DomU Client Performance
>
>
> > >
> > > NFSServer1 - Standard FC5 box (ie no Xen)
> > > NFSServer2 - Xen based DomU FC5 box (exactly the same as
> > > above but runs as a
> > > DomU)
> > >
> > > DevClient1 - Standard FC5 box
> > > DevClient2 - Xen DomU FC5 box
> >
> > I have no suggestions, but I would like to know if you''ve
> > tried to see what is different between the two ways to
> > connect by using for example tcpdump to see what the network
> > traffic between the two machines look like in the different cases.
> >
> > Also, what''s the configuration of your NFS server machine:
> > What type of processor, number of cores, amount of memory
> > (Dom0 and DomU memory setup in the Xen case).
>
>
>
> >
> > It may be that with this information, the problem can be
> > solved quite easile [but it may also be that it can''t - I
> > haven''t played with any of the above parts, so I
don''t know...]
> >
> > --
> > Mats
>
> Hi Mats,
>
> Will try and answer as well as I can.
>
> #TCPDUMP
> Strange...
>
> With a Xen client, I get seemingly standard traffic (bar a
> few checksum
> errors) and then it seems to hang for 105seconds (I guess how
> long I seem to
> wait) and then it carries on as normal.

Checksum errors... That may mean that the packet is discarded by the
recipient, which in turn means that it requires re-transmission by the
sender, which happens some arbitrary time later, say 105 seconds,
perhaps?

I''d like to suggest you search this mailing list for "checksum
offloading" to see if this helps your problem.

--
Mats