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RAM Provisioning and x64 OSes

Don't get me wrong. I am really excited for the recent updates to VMware and Microsoft recently. With Windows Server 2008 R2 and VMware's vSphere Update 1 being released, this is a good time for a facelift to the modern data center.

vSphere Update 1 brings a lot of new features to the table, but Windows Server 2008 R2 and Windows 7 support are where I am focused now. What concerns me is now that Windows Server is 64-bit only (x64), we may run into higher memory provisioning scenarios. For 32-bit (x86) Windows OSes, the memory limits were a softer 4 GB for Windows Server 2003 x86 Standard Edition and select editions of the x86 Windows Server 2008 base release.

With Windows Server 2008 R2, x86 is dead in favor of x64 only. So, gone, too, is our 4 GB limit for RAM for the Standard editions of Windows Server, which, in many data centers, is the most common operating system. Now that virtualization is very comfortable in the data center, will we see a higher number of virtual machines with assignments greater than 4GB? I'm not sure, and every environment will depend on many factors.

What does this really mean? Primarily, it can be a consolidation ratio killer. In my virtualization practice, the occasional virtual machine with 4 GB of RAM was not uncommon but was definitely not the norm. If the occasional 8 or 12 GB of RAM virtual machine start to show up in the mix, I would start to get concerned about my host provisioning practice. As of late, I am sure we all have enjoyed relatively low costs for RAM in virtualization hardware, but I am not sure that will be the case forever.

For VMware environments, we still can rely on the memory management technologies such as the balloon driver and transparent page sharing. But, I don't want to rely on those as a host-provisioning practice.

How are you approaching large RAM virtual machines? Share your comments below.

Posted by Rick Vanover on 12/01/2009 at 12:47 PM


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