I understand from the VMware Server 2 documentation that VMware Server 2 is capable of running a 64-bit guest OS underneath a 32-bit host OS, as long as the hardware running the box is 64-bit capable.
Here's my situation. We currently have an underutilized XEON X3220 Quad Core 64bit Server, running Server 2003, 32-bit and 2gb of RAM (the motherboard is capable of 8gb ram). The server is currently used mainly for file and print services. It is also running Active Directory, Novell eDirectory and Groupwise 6.5. We are planning a micration to Microsoft Exchange, so the Novell eDirectory and Groupwise services will eventually be purged from this box, leaving only Active Directory, File and Print services.
Being that this server is underutilized we are hoping to save hardware costs and virtualize our new Exchange investment. My question is this. Will VMware allow access to the "invisible" extra memory that Windows 32-bit won't see. Meaning, if we increase the full amount of system ram to 8gb (yes, I know the 32-bit host OS will only see a maximum of 4gb), will I be able to assign maybe 5gb to the new Server 2008 64-bit OS running Exchange and leave 3gb for the Guest OS (or maybe even a 6, 2 split).
The second part of that would be, would it be better to just convert the main OS currently running to an image, convert the machine itself to ESXi and run both OSes as images under ESXi.
Downtime for this box is critical, so my preference is most definitly with the first option because it presents very minimal downtime. Doing the second would make downtime quite a few hours to image the machine and then convert the image to a VMware Image.
Don't piddle with Server 2. Here's what I'd do... build-up an ESXi4 box (will require 64-bit processor and 4gb ram), and then use the coldclone.iso (a.k.a. P2V, or Physical To Virtual) to migrate your eDirectory/GroupWise/AD server off of its current hardware. Then, install ESXi on that hardware, and move the virtual machine off the temporary ESX host (e.g. FTP) Total, you'd be able to do this in an eight-hour day (not counting downloading ISO files.) The result would be, your existing hardware could see the full 8gb of ram the board is capable of, AND it'd be able to use it for your proposed Exchange migration -- which will be greatly aided by the use of snapshots and the like.
You can build-up an ESX box suitable for this purpose using a high-powered desktop (e.g. 64-bit processor + 4gb ram + storage to replicate your physical disk used on the current directory server.) I do this quite routinely. The only real caveat is that you need to have a disk controller and network card supported by ESXi. I used a Promise SATA300 on my home ESXi server. Works like a champ!
Cheers, -C
Given your plans I'd strongly urge you to move to ESX now, that way you get all of the machine's resources today, you can stick with your 2K3 32 VM and start work right now on building out your new systems without risking your current environment.