Xen and the art of Database performance

[McDougall, Marshall (FSH)]

A while back we took delivery of several Dell 2950 servers to update our
hardware environment which supports our Ingres, Sybase and DB2 systems.
Ingres 2.6 and DB2 were running on RHEL 2.1, Sybase was running on
RHEL3.  We were hoping to be able to maintain the same levels software,
but the new hardware is not supported by RHEL2.1.  This is where the fun
starts.  I built up several RHEL4 servers and installed the Database
systems on them and gave them to the DBA's to test.  They promptly came
back and said that they were up to 7 times slower than the previous
hardware platforms, with the exception of DB2.  I ran some OS benchmarks
and they came back up to 7 times faster than the previous hardware.  We
worked on various tweaks and tunes to the OS and DBMS to no avail.
At that point we started to engage the vendors/support orgs for the
various products.  Sybase could do nothing to improve performance on the
RHEL4 server, so we tried RHEL5(or advanced platform or whatever they
are calling it this week). The performance was just as dismal.  We ended
up going back to RHEL3U9 to get the Sybase environment to an acceptable
performance level. 
Ingres is another story.  First they said try Ingres 2006.  It worked,
but it has significant implications to our OpenRoad development
environment, and as such is not really an option.  I went the same route
as before with the various flavours of RHEL and it made no difference.
Finally, I built a RHEL5 server, installed VMWare Server, and created a
RHEL2.1 guest on that.  We now have performance where we want it.  The
downside is that on my server with 8GB of ram I can only use 3.6GB for
the VM. 
My options as I see them now are; Install VMWare ESX and see if that
buys me anything, or spend the time and effort to see if Xen will be of
benefit.  The problem with the latter is that according to the doc RHEL
2.1 is not a supported OS on RH5.  

So, after all this,  the gist of my post is; Has anybody successfully
sparked up a RHEL 2.1 guest, using more than 4 GB of RAM, on a RH5
virtual platform, or, has anyone installed Ingres 2.6 on a Linux 2.6
kernel and made it perform at an expected level?  Thanks for reading
this far.

Regards, Marshall