I recently installed a hp server 2008 sbs 64 bit server.Dual xeon ,16gb ram ,raid 5 etc.
Whats happening is after a couple of days all free physical memory (ram) is being cached leaving nove free for the server itself. ie this is mainly ised as a file server and daily file operations are being cached and its leaving no free ram for the server itself ,to run backup exec etc. This is evident from by very slow opening times on any application on the server. a reboot sorts everything for a while.
I have read loads on the web and ppl suggest creating a service called dynamic caching but this seems to have no effect,