I have an ESXi 5 installed on Dell poweredge r610 with 48GB ram, 2XIntel Xeon E5606Processor (2.13GHz 4C, 4X1TB N.L SAS 6Gbps 7.2k 2.5" Additional HD)
I manage the server through vCenter (essential license) and installed 2 windows server 2008 r2 machines:
1. DC with 8GB ram and 2 CPU virtual sokets with 1 core per soket
2. Exchange 2010 16 GB ram and 4 CPU virtual sokets with 1 core per soket also 1TB of virtual disk (2 partitions 100g system & 900g for exchange db)
Suddenly from an unknown reason the second machine with the exchange installed on hits 100% CPU and become unreachble - no ping, no consol, no RDP - NOTHING
aftre a lot of research and digging in we found a something about mmc.exe process that using a lot of CPU, i'm not sure it's the main problem cause we have more servers in the network like server 2008 sbs which was the main server in the company and now we taking it out but slowly, we first took out the exchange from it and now the AD & DNS, anyway we have new AD DC on a different phisicaly server (also server 2008 r2) totaly new that holds all the FSMO rules - the new DC is not on the ESXI.
the exchange server is freezing with 100% cpu every few days, sometime in the middle of the night and sometime in the middle of the day no metter what we're doing - there is no connection between the crashes,
Check the counters within the vcenter console as well. Make sure that there is no issue with the host side providing the resources. Such as resource pools restricting anything, etc. I would even try taking the number of CPUs on the Exchange server down to 2 as a test, or assign it a specific physical CPU on the host through vCenter (been a while but I believe you can do that).