Memory Sizing Exchange 2007

Been up and down reading articles so I give up and gonna ask!

Vmware vSphere 4.0 host with Windows Server 2003 x64 and Exchange 2007 running Mailbox, Hub and Transport roles.  

Current VM config is: 2 Virtual CPUs, 4gb Ram.  Current CPU usage for a half a day is about 30% and 55% of allocated ram.  Performance Monitor shows heavy Page File reads, server performance feels slow and Outlook users frequently advise of poor performance.

According to Microsofts "Best Practices" based on memory sizing I calculate I should allocate 10gb of ram, so I did.  Thus far all seems OK, but Vmware states of the 10gb I allocated merely 10% is being used for Guest Mem on the host.

Maybe I am prematurely writing this, but so far it appears Vmware recommendations and Microsofts conflict. I would love to not allocate so much ram, but fear heavy Page File Reads which *may* increase latency for that iSCSI storage node.

Any ideas or should I wait for a full days use and see what happens?

vhatoAsked:
Who is Participating?
 
Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
If you feel, after extensive monitoring, your virtual machines are not needing that amount of RAM, the beauty of Virtualisation is you get take it away and reallocate elsewhere (you need to turn off the VMs, and schedule downtime). A little bit more difficult with a physical machine, you can also be a lot more granular with memory allocations as well. You don't have to work in 512MB or 1GB chunks because thats thinking physical DIMMs!
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coolsport00Commented:
VMware recommendations for 'resources' will mirror the applicable application, server OS, etc. specs. I have the same setup as you and have 6GB of RAM, which I believe is the recommended amt. But, I only have about 250-300 users. Amt of users plays a bit of a role in resource config as well. I would suffice to say that if you backed up your RAM a couple GB at least, you'll still be fine.

Regards,
~coolsport00
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vhatoAuthor Commented:
And I agree with you...but why allocate so much memory when Vmware shows i only need 10%?
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coolsport00Connect With a Mentor Commented:
You need to allocate memory the application/software is requiring. VMware may not see it as being much, but Exchange does need 6GB+ memory to function properly.

~coolsport00
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