Exchange 2010 – Stopping the Information Store Service does not failover database copies.

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In Exchange 2010 we achieve high availability of mailbox databases by utilizing a Database Availability Group (DAG).  When a DAG is utilized, and mailbox database copies are created on DAG members, they are either MOUNTED (active) or have a copy status – for example HEALTHY (passive).

If an administrator or another process gracefully stops the Information Store Service on a DAG node, any database copies that were mounted on that server enter a DISMOUNTED state.  These copies do not fail over to another node, as the shutdown was graceful and not the result of an error condition that would trigger a failover event to occur.  Should the processed have crashed or otherwise became unavailable, this would be detected as an error and the database instances failed over.

Let’s take a look at this.

In this environment I have a four mailbox server DAG.  Database DAG-DB0 is replicated to all members of the DAG.  Currently DAG-DB0 is mounted on mailbox server DAG-1.

Get-mailboxdatabasecopystatus *\DAG-1

Name Status
---- ------
DAG-DB0\DAG-1 Mounted
DAG-1-DB0\DAG-1 Mounted
DAG-DB1\DAG-1 Healthy 

On DAG-1 I issued a net stop msexchangeis.  This gracefully stopped the Information Store Service.

Log Name: System
Source: Service Control Manager
Date: 3/21/2010 11:27:19 AM
Event ID: 7036
Task Category: None
Level: Information
Keywords: Classic
User: N/A
Computer: DAG-1.domain.com
Description:
The Microsoft Exchange Information Store service entered the stopped state.

Reviewing the mailbox database copy status for DAG-1, the following is noted.  (Get-mailboxdatabasecopystatus *\DAG-1)

Name Status
---- ------
DAG-DB0\DAG-1 Dismounted
DAG-1-DB0\DAG-1 Dismounted
DAG-DB1\DAG-1 Healthy 

As a response to the IS gracefully shutting down the mailbox database copies that were mounted on that host are now dismounted.

Subsequently I issued the command net start msexchangeis to start the Information Store Service. 

Log Name: System
Source: Service Control Manager
Date: 3/21/2010 11:34:18 AM
Event ID: 7036
Task Category: None
Level: Information
Keywords: Classic
User: N/A
Computer: DAG-1.domain.com
Description:
The Microsoft Exchange Information Store service entered the running state.

After restarting the service the databases that were previous dismounted are now mounted.  (Get-mailboxdatabasecopystatus *\DAG-1)

Name Status
---- ------
DAG-DB0\DAG-1 Mounted
DAG-1-DB0\DAG-1 Mounted
DAG-DB1\DAG-1 Healthy