Recently I had the (un)fortunate experience of troubleshooting an issue with Exchange 2010 DAG Database copies failing over to another servers. This happened in several different environments that I was supporting, so I know it can happen to anyone. Here is a short synopsis of this issue (not all symptoms are listed):
Our Resolution: Step 1: Confirmed that all servers within the DAG were consistently and properly configured, specifically network configuration and antivirus exclusions Step 2: Installed latest drivers, firmware, and recommended hotfixes (2 fixes resolved memory leak issues) Step 3: Added additional RAM in the servers (amount may vary on environment/need) Step 4: Reboot the server
NOTE: Prior to modifying the RAM of an Exchange 2010 server, understand how that will directly impact database cache. Review Understanding the Mailbox Database Cache. Also understand that other factors may need to be adjusted (ex: paging file config).
Some may ask, “didn’t you follow the RAM guidance within the mailbox storage calculator?” Yes we did but there were several factors that changed after we completed that phase of the design, including mailbox configuration, additional processes running on the servers, and user profiles/load.
Good Luck! Doug