Q. Which OSs support hot addition of memory?

A. Hot adding memory allows you to add memory to a running operating instance without a reboot. This applies to both OSs installed on physical hosts and those in virtual environments.

OSs that support hot-add are listed below. Note that the version listed and higher versions are supported—Windows Server 2003 is listed, so Server 2003 SP1, SP2, and so on also support the feature.

• Server 2003 Enterprise and Datacenter x86
• Server 2003 SP1 Enterprise and Datacenter x64
• Server 2003 SP1 Itanium
• Windows Server 2008 (and R2) Enterprise and Datacenter x86 and x64 and Itanium

Note that none of these OSs support the hot-removal of memory.

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• Q. I heard that VMware ESX allows you to overcommit memory, which means it pages out the memory of guests to a file, giving very poor performance. Is this true?
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