Exchange DB DAG 2013 activation preference change

Claude_Cardinal used Ask the Experts™
I have an exchange server 2013 DAG install at my workplace.

I have 2 CAS server and 2 Mailbox server.

there is 14 DB

MBX1 was always the preferred  active server for the 14 DB but for a reason that i don't understand is that the 14 DB are now balance between MBX1 and MBX2 meaning 7 DB on MBX1 and 7 DB on MBX2.  

MBX1 is the active preference with a value of 1 and MBX2 is with a value of 2. What could be the issue. The mail server works and I saw that it is best practice to keep everything in balance with the DB,

This just happen two weeks ago for no reason.

How can we explain that behavior.
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Alan CoxSr. Architect | Consulting

does it fail back to MBX2 if you manually activate on MBX1? did you run any auto balance script?
You might need to run collectovermetrics.ps1 script.
about 2/3rd of the way down.
Saif ShaikhServer engineer

If there are 14DB's in DAG then with administrator intervention only these databases can be balanced across different nodes. Automatically not possible.

You need to check the crimsons logs for database fail overs and what caused the issues which will provide more information on database fail overs.

1. Open Event Viewer.

2. In the console tree, navigate to Applications and Services Logs > Microsoft > Exchange.

3. Under Exchange, select a crimson channel, such as HighAvailability or MailboxDatabaseFailureItems to see DAG and database copy-related events, or ActiveMontoring or ManagedAvailability to see events related to Managed Availability.

The HighAvailability channel contains events related to startup and shutdown of the Microsoft Exchange Replication service, and the various components that run within the Microsoft Exchange Replication service, such as Active Manager, the third-party synchronous replication API, the tasks RPC server, TCP listener, and Volume Shadow Copy Service (VSS) writer. The HighAvailability channel is also used by Active Manager to log events related to Active Manager role monitoring and database action events, such as a database mount operation and log truncation, and to record events related to the DAG's underlying cluster.

The MailboxDatabaseFailureItems channel is used to log events associated with any failures that affect a replicated mailbox database.

The ActiveMonitoring channel contains definition and result events for Managed Availability probes, monitors and responders.

The ManagedAvailability channel contains recovery action logs and results and related events.


This is what i saw

Event Logs - Applications and service - Microsoft - Exchange- High Availability - Network

Database scanning during passive replay is disabled on 'Database'. Explanation: Availability at risk. ReplayQ= XXX

for each of the 7 DB

can i use this command to put it back the way it was:

Set-MailboxDatabaseCopy -Identity DB1\MBX1 -ActivationPreference 1

Should this be done outside of business hours?
Saif ShaikhServer engineer

Check the cluster event logs for any cluster failovers.

Event viewer - System event logs.
We finally saw that a firmware update was done on the SAN where the MS Exchange disk are attach. I have move back the DB to the MBX1. Everything looks to be working good now.

Did a Test-ReplicationHealth and Get-MailboxDatabaseCopyStatus to test the DAG and it looks great

I saw some warnings that happen in the Vsphere and in Windows logs.

thx to all for your help.

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