Xen and the art of Database performance

McDougall, Marshall (FSH) Marshall.McDougall at gov.mb.ca
Thu Oct 25 13:42:41 UTC 2007

>-----Original Message-----
>From: redhat-list-bounces at redhat.com 
>[mailto:redhat-list-bounces at redhat.com] On Behalf Of J. 
>Refugio Rodriguez
>Sent: Wednesday, October 24, 2007 2:59 PM
>To: General Red Hat Linux discussion list
>Subject: Re: Xen and the art of Database performance
>--- "McDougall, Marshall (FSH)"
><Marshall.McDougall at gov.mb.ca> wrote:
>> 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.
>Indeed, XenSource does not include the appropriate
>modified kernel for RHEL 2.1 and, accordingly, is not
>officially supported on XenEnterprise 3.2 or higher.
>Notwithstanding, you can create an proper Linux kernel
>for your RHEL 2.1 by installing the same into a
>machine that has the CPU virtualization extensions
>(i.e., hardware assisted virtualization).
>Once you successfully install/modify your RHEL 2.1
>under XenEnterprise in the above hardware assisted
>virtualization environment, you can use the image on
>older non-hardware assisted virtualization CPUs.
>Before going to ESX, you may want to evaluate
>XenEnterprise in price and performance.  Back in
>version 3.2 of XenSource XenEnterprise, you could
>allocate to an virtual machine up to 15GB of memory.
>Disclaimer: Metztli Information Technology is an
>Xensource Certified Partner.  
>> 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
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>Jose R Rodriguez
Thanks for the input Jose.  It sounds like it's doable with Xen, but it
also sounds like it's painful.  Yesterday I downloaded a time bomb trial
of ESX and had it and a RHEL2.1 VM running in about 1.5 hours.  I've
taken a lot longer than that just trying to understand the Xen docs that
I can find.

Regards, Marshall

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