I have a question regarding the activation preference number on database copies in Exchange 2010. I was hoping that this feature would allow us to weight DB copies on servers so that in the event of a mailbox server outage, we could control the failover behavior (eg. which server will activate its DB copy). However, this feature doesn't seem to be working as expected in our environment. We have had a few failure scenarios occur, and it seems somewhat random what mailbox server activates its DB in the event of a failure. We have seen servers with the highest preference number come up as active about as often as ones earlier in the sequence, and many times one with a higher number will become active even though there are several servers higher in the sequence available. What gives? Is there anything else in the Exchange configuration etc. we need to look at? Is this just not how this feature works? Does this only apply to switchovers (eg. vs. failovers)? Thanks for the help!

Just because you set an Activation Preference on a database doesn't necessarily mean you'll get your will put into action. Active Manager in DAG uses some criteria for selecting the best database for activation. You cannot bypass this, but rather tell the Active Manager that if a tie arises in the selection, please go ahead and mount the databases in the foolwing order. " Which of my 300 database copies are you going to mount up then?? - Active Manager Best Copy Selection Criteria When a failure affecting the active database occurs, Active Manager calls several sets of selection criteria to determine which database copy should be activated. Active Manager attempts to locate a mailbox database copy that has a status of Healthy, DisconnectedAndHealthy, DisconnectedAndResynchronizing, or SeedingSource, and that meets all of the following criteria: It has a content index with a status of Healthy. It has a copy queue length less than 10 log files. It has a replay queue length of less than 50 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Crawling. It has a copy queue length less than 10 log files. It has a replay queue length of less than 50 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Healthy. It has a replay queue length of less than 50 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Crawling. It has a replay queue length of less than 50 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a replay queue length of less than 50 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Healthy. It has a copy queue length less than 10 log files. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Crawling; and It has a copy queue length that is less than 10 log files If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Healthy. If none of the database copies meet all of the preceding criteria, Active Manager tries to locate a database copy that meets the next set of criteria: It has a content index with a status of Crawling. If none of the database copies meet all of the preceding criteria, Active Manager tries to activate any database copy with a status of Healthy, DisconnectedAndHealthy, DisconnectedAndResynchronizing, or SeedingSource. If it can't find any database copies with this status, it isn't able to automatically activate a database copy. In each of the preceding passes, if more than one database copy meets all of the preceding criteria, the configured value for ActivationPreference is consulted, and the database with the lowest value is activated and mounted. " More here: DAG Active Manager Deep DiveJesper Bernle | Blog: http://xchangeserver.wordpress.com

Understood. The thing is that in our environment, every other passive database was in Healthy status and had copy and replay queue lengths of zero immediately prior to the failure event. Even in this scenario, the DAG still seemed to ignore the activation preference number set on the DB copies. Anything else I should look at?

How about the “Content Index State”? Whether it’s the exchange 2010 RTM or SP1? Please make sure that the “AutoDatabaseMountDial” is set to “Loseless” (Set-MailboxServer), which will sort the list by using the value of ActivationPreference Understanding Active Manager James Luo TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

I'm not sure about the content index state. All I know is that the DB copies showed "Healthy" in the Exchange admin console. We're running Exchange 2010 SP1 with hotfix rollup 2 installed. You bring up an interesting point with the AutoDatabaseMountDial. Currently, this is set to GoodAvailability on each of our mailbox servers, which must be the default in Exchange 2010 because we haven't changed it. Do you recommend changing this to Lossless? Will this allow us to better control how these failovers behave? Thanks again for the help!

In the link posted above, you can find the words below: “In Exchange 2010 Service Pack 1 (SP1), the behavior is the same as in the RTM version, except for servers configured with an automatic database mount dial value of Lossless” “Lossless” will make Active Manager to use Activation Preference as the primary sorting key, and then the list of the available database copies will be enumerated by the priority of Activation PreferencePlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Perfect, that's exactly what I needed. Thanks for the help!