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Re: [Xen-users] MSSQL and Xen performance

To: blackc2004 <chrisb@xxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] MSSQL and Xen performance
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Sat, 9 May 2009 20:53:50 +0300
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On Fri, May 08, 2009 at 08:46:37AM -0700, blackc2004 wrote:
> Thanks everyone for the tips!
> Unfortunately I didn't get to "pick" the consultants, they came with the
> company that is doing our new ERP installation. So far I have not been happy
> with the way things are going.
> I am running:
> Xen 3.1.2-128.1.6.el5
> CentOS 5.2
> PowerEdge 2970 (2) Quad Core Opteron 2344HE, 4x512K Cache 1.7GHz, 1Ghz
> HyperTransport
> I have given 5 VCPUs and 4 gigs of RAM to the MSSQL Server, I was planning
> on increasing that within the next week.
> The storage backend is via iSCSI to an Equallogic PS5000.

You could also run MS iSCSI initiator in the Windows HVM guest.. to be able
to use EQL snapshots for MSSQL etc. But you really need those paravirtualized 
(GPLPV) drivers for the virtual NICs :)

-- Pasi

> Since this is a brand new MSSQL installation (and we have never had one
> before), I do not know what the load will look like for us.
> I have been noticing some network performance issues in early testing and
> will be implementing some changes to the severs this weekend to see if those
> are resolved. I will also be looking into the GPLPV which have been
> suggested!
> Thanks again
> Dustin Henning wrote:
> > 
> > Another important note regarding using Windows on Xen:
> > I am pretty sure that using multiple CPUs causes severe performance loss
> > with the GPLPV drivers provided by James Harper (to the extent that having
> > one VCPU with the drivers may net better performance than having
> > multiple).
> > However, I believe the GPLPV drivers still provide better performance with
> > multiple vcpus than not having the drivers would.  This information could
> > be
> > slightly dated, but I believe it was recently mentioned by someone else on
> > the list.  Regardless, some testing of your scenario options would be duly
> > diligent.
> >     Dustin
> > 

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