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Re: [Xen-users] Poor NFS Perofrmance on Dom0 Storage to native DomU

  • To: peter.chiu@xxxxxxxxxx
  • From: Ciprian Dorin Craciun <ciprian.craciun@xxxxxxxxx>
  • Date: Sat, 7 May 2011 19:35:57 +0300
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
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On Thu, Apr 28, 2011 at 21:33,  <peter.chiu@xxxxxxxxxx> wrote:
> I set up Dom0 and a couple of DomU all with Suse Enterprise 11 SP1 on a DELL 
> PowerEdge R710.
> I then NFS export a SATA 2TB disk on Dom0 to the 2 DomU guests.
> >From the 2 DomU guests, I can only get about 2MBytes/s using dd tests (with 
> >dd if=/dev/zero bs=1M count=1000).
> I doubt the problem is on NFS, because I set up similar Dom0 and DomU on two 
> other DECLL PowerEdge R710s.
> >From these DomUs, I can get about 90MB/s on the same NFS mounted storage.
> So the problem seems to be relating how the Dom0 communicates with its native 
> DomU guests.
> I check this using iperf, but found their speeds are in multiple of Gbits/s 
> in both directions -
> the Dom0 has a 10G dual port Ethernet card. ÂIperf also give similar figures 
> with DomUs from other physical servers.
> I checked through the Suse Enterprise doc on virtualisation, but cannot find 
> any clue to explain why that is the case.
> Does anyone has any idea why?
> Thanks.
> Peter

    I suspect I've hit the same problem some time ago with a Gentoo
based dom0 and domu (Xen 3.4.x i think).

    But in my case the problem was even worst as the domu froze.
Initially I've used NFS over TCP, and when I've switched to UDP and at
least it didn't freeze. But the write performance is still impacted.
(I've not investigated any further as I'm using the NFS for sharing
the Gentoo portage directory, which is now read-only on the domu).

    Please tell me if you've found the problem / solution.


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