Over the last few years, memory has become increasingly inexpensive. As a result, for scalability, you can often see Exchange servers with 64GB or 128GB of RAM.
In the past, Microsoft's guidance on pagefile size has been system memory plus some amount to allow for the contents of memory to be written to disk in the event of a crash. Basically, this is for troubleshooting information. For Exchange 2013, the guidance has been RAM+10MB.
Unfortunately this means that a large amount of disk space is used for that pagefile with little benefit because it's not typically used much. Certainly not the full RAM of the system. I've been arguing for a long time that unless you are troubleshooting bluescreen events with Microsoft support, there is no need for this large of a pagefile for Exchange or regular Windows servers.
As of Exchange 2013 SP1 the new guidance is to max out the pagefile at 32GB+10MB. Apparently Microsoft has been doing this internally for some time.
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