How many servers does the MSN Messenger service run on?
The MSN Messenger server farm handles over 70 million concurrent sessions every single day. When they switched to Windows Server 2003 x64 Edition running on x64 hardware, they reduced the size of the farm from 250 32-bit servers to just 25 servers. The company had seen a 10-times performance gain from the MSN Messenger servers since they went 64-bit.