We often think how to Move Exchange Server 2016 to Different Active Directory Site. This kind of situation arises when you plan to extend the Messaging Infrastructure DR for Site resilience. Replicating small databases are possible by installing Exchange Server in DR site, however it may not be viable option replicate databases over narrow bandwidth if we plan to host bigger databases. From Exchange Server 2010, we can easily shift/move exchange server one active directory site to different AD Site by following simple steps outlined below.

1.  Ensure that you have created and replicated required AD site and Subnets for DR/Secondary datacenter.

AD Site Details

2.  Ensure that the Exchange Server Infrastructure is healthy, and all the databases are replicated properly.

DB Copy Status

3.  It is also recommended to check the AD and Exchange replication help using,

Test-ReplicationHealth from DR Exchange Server & nltest from DR Domain Controller

4.  Verify the current AD site status of Exchange Server

Before Moving Site Info

Before Moving Exchange Server Site Info

5.  Now we are good to initiate the server site migration. Before we shut down and physically move the server to different site, it is recommended to set the Exchange Server to Maintenance Mode.

.\StartDagServerMaintenance.ps1 -serverName EX16-DR1 -MoveComment SiteChange

And check the cluster status

Get-ClusterNode | ft name, dynamicweight, nodeweight, state -AutoSize

Move it to Maitenance

 

6.  Shutdown and Shift the server to new site (DR/Secondary data center) and Bring up the server with new IP range configuration (subnet should be aligned to DR site).

7.  Restart the Server once again to register required DNS entries and other connectivity.

8.  Follow the below commands and ensure that the site movement of DAG member is success

Get-ClusterNode | ft name, dynamicweight, nodeweight, state –AutoSize

And if the status is Pause, then everything is fine. If the status is Down, that means some connectivity issues, please continue to troubleshoot.

Get-ExchangeServer | select Name,Site

Ensure that the site has changed, if you find the value that you expect then proceed to remove the server from maintenance mode.

.\StopDagServerMaintenance.ps1 -serverName EX16-DR1

The server status will change to Up from Paused post this step, and it will begin to replicate the delta and eventually the database copies will become healthy.

Final Stages

 

That’s it,  you have completed the AD site change for Exchange DAG Member/Node.

Share you experience in the form of comments, we will deal whichever possible.

-Praveen

Published in Solutions

You may experience similar problems in version from Exchange 2010, here I have showcased an issue I faced in Exchange Server 2016 infrastructure.

You will see one or more of the following events/status on the server,

Event IDs 4026, 1009 etc.
Log Name:      Application
Source:        MSExchangeRepl
Event ID:      4026
Level:         Error
Computer:      ex16-01.lab.ed.com
Description:
[Seed Manager] The seed request for database 'LAB-DB01' encountered an error during seeding. Error: An Exception was received during a FAST operation.

 

Log Name:      Application
Source:        MSExchangeFastSearch
Event ID:      1009
Task Category: (1)
Level:         Warning
Computer:      ex16-01.lab.ed.com
Description:
The following information was included with the event:
LAB-DB03
Microsoft.Exchange.Search.Core.Abstraction.OperationFailedException: The component operation has failed. ---> Microsoft.Exchange.Search.Engine.FeedingSkippedException: "Feeding was skipped for '45fc6bd2-7221-4c3d-8314-4e6e75473703 (LAB-DB03)' due to the state 'Unknown', error code: 'Unknown'."
 
FailedAndSuspended

Explanation:

This issue can cause due to many factors, and most cases it can be mitigated by Solutions mentioned in the next section.

The reasons for this issues could be one or more of the following, but not limited to

  1. Issues with “Microsoft Exchange Search” (MSExchangeFastSearch) Service
  2. Issues with “Microsoft Exchange Search Host Controller” (HostControllerService) service.
  3. Corrupt Content Index
  4. Hard disk errors (read/write)

How to mitigate this issue, follow as suggested below!

Solution 1

Generally, this issue can be mitigated in one of the two list options below,

Option 1:

Consider you do not have any database copies with healthy Index State or the only server that host the database.

Stop the following services,

Microsoft Exchange Search Host Controller
Microsoft Exchange Search

Delete the folder similar to the following from database path/location.

Delete Folder

Start the Services in order,

Microsoft Exchange Search
Microsoft Exchange Search Host Controller

The Exchange Server will initiate the process to rebuild the whole index. Depends on the data/size the process may take extended period of time. Wait for the process to finish, and in 90% of the case it will fix the issue.

Option 2:

If you have one “healthy” Content Index state database copy, reseed the database copy that has the unhealthy copy of content Index. In some cases when you add database copy in the DAG, the content index can go into unhealthy status (such as failed, unknown, failedandsuspended etc). To recover the content Index back to healthy, you can reseed the content index by running the “Update-MailboxDatabaseCopy” command with switch “-CatalogOnly”.

Update-MailboxDatabaseCopy LAB-DB03\EX16-01 –CatalogOnly

If you already tried this command, you may get the warning “Seeding cannot be requested for the same database copy until the failed request has been cleaned up by the server …”. Please say “y” to proceed with the reseed operations.

Verify the ContentIndexState after sometime, you will see a “healthy” state.

Solution 2

If the above steps did not go through fine, and if you receive errors similar to below even if all these services are healthy then it will be not an easy task to bring back your ContentIndexstate to healthy.

WARNING: Seeding of content index catalog for database 'LAB-DB03' failed. Please verify that the Microsoft Search (Exchange) and the Host Controller service for Exchange services are running and try the operation again. Error: An error occurred while processing a request on server 'EX16-03'. Error: An Exception was received during a FAST operation..

In some cases, there are disk errors but in my case the server was recovered from a unexpected failure which lead to run recovery steps on the database. Post the recovery the ContentIndexState was in healthy status in some database copies, but did not work quite fine in others.

Please note that the Content Index State only impact the end user experience, you are still allowed to mount the database on server where the Content Index State is not healthy. Hence the recommended approach is to create additional database and move the mailboxes gradually to get rid of the problematic database.

In my case, I also had the following event (Event ID 40025) logged on the server where this database was active.

 
Source:        MSExchangeIS
Event ID:      40025
Task Category: High Availability
Level:         Error
Computer:      EX16-03.lab.ed.com
Description:
       Database LAB-DB03 (45fc6bd2-7221-4c3d-8314-4e6e75473703) has been offline-repaired (by eseutil.exe) one or more times in the past. However, although this ensures database-level logical consistency and may permit the database to be successfully mounted, Exchange-level logical consistency can no longer be guaranteed. Therefore, all mailboxes should be evacuated from the database and the database should be retired as soon as possible in order to eliminate the potential for unexpected behaviour caused by Exchange-level logical inconsistency.      
This event will continue to be emitted once per hour while the database is mounted as an urgent reminder to evacuate and retire the database as soon as possible.      
Database last repaired: 3/15/2017 7:04:00 AM      
Repair count since the database was last offline-defragmented: 2      
Repair count before the database was last offline-defragmented: 0      
Recovery database?: False    
 
Please note that the above events and actions are based on Exchange Server 2016 infrastructure, however the operations are almost stays the same in other versions from 2010 onward.

Please share you comments or issues.

-Praveen

 

Published in Solutions

You may receive the following error when you tried to re-add a recovered Exchange 2016 Mailbox server back to Database Availability Group (DAG).

-
A server-side database availability group administrative operation failed. Error The operation failed. CreateCluster
errors may result from incorrectly configured static addresses. Error: An error occurred while attempting a cluster
operation. Error: Node EX16-01 is already joined to a cluster..
-

You may also see that the following error when trying to run the command "Set-DatabaseAvailabilityGroup". Please note I ran the command from the cluster node which I was trying to add to DAG.
-
The following servers in the Windows Failover Cluster are not in Active Directory: ex16-01. This is usually the result
of an incomplete membership change (add or remove) of the database availabilty group.
-

The above error usually the result of disabled cluster service, or AD replication errors.

Solution:

It is evident that, some stale entries or communication error stops from adding recovered exchange server to the DAG cluster. Before you start any process to forcefully remove or add, try to do a force replication of Active Directory and repeat the usual procedures. If the results are same, follow the below process.

Run the following command from a healthy DAG Member.

1. Forcefully Remove cluster node which you failed to join the DAG cluster. In my case, I was trying to re-add the node ex16-01 back to the DAG02 Database Availability Group.

Get-ClusterNode ex16-01 | Remove-ClusterNode -Force

Wait for 10 - 15 minutes, so that the replication happens.

2. Run the command Add-DatabaseAvailabilityGroupServer with the node we want to add to cluster.

Add-DatabaseAvailabilityGroupServer -Identity DAG02 -MailboxServer EX16-01

3. Verify the Database Availability Group status,

[PS] C:\Windows\system32>Get-DatabaseAvailabilityGroup DAG02 | fl Name,Started*

Name : DAG02
StartedMailboxServers : {ex16-01.lab.ed.com, EX16-03.lab.ed.com, EX16-02.lab.ed.com}

Following screen shot shows the chronology for your better understanding.

Chronology


Post this, you may proceed with adding database copies or additional cluster operations.


-Praveen

Published in Solutions

By now we are familiar with the concept of DAG. Database availability group is nothing but a set of up to 16 Exchange Server 2016 mailbox servers that provide high availability or automatic database recovery database-level recovery from a database level. It is an improved clustering operation from Exchange Server 2010 onwards. I recommend you to read more about DAG if you are not familiar with, as this article gives only an insight to DAG creation and database copy configuration.

Create Database Availability Group

1. Open Exchange admin center (EAC), and navigate to Servers

2. Click on Database Availability Group on the right pane of the console

3. Click on + sign to add DAG

4. Enter the required information such as DAG Name, Witness Server, Witness directory IP address etc. and click on Save button

Note: If you plan to use a domain controller as witness server, please add it to the Exchange Trusted Subsystem security group. In addition, add the Exchange Trusted Subsystem into the Administrators group

EAC - 1

This will create a Database Availability Group for you Exchange Server 2016 server.

DAG - EAC - 3 1

Add Members to DAG

1. Select the DAG name and click on Manage

2. Save once you add all required servers.

3. Now you can add database for High Availability.

DAG - EAC - 4

Note: The process will take some time, as the failover cluster feature will be installed during the member addition process. Please wait patiently until the operation is finished.

Add Database for High Availability

1. Create Database on one of the DAG Members (follow the usual steps)

2. Select the Database for which you need High Availability, and click on Add database copy from more option.

[Note: You might require to re-login to EMC in case if you did not find the Add database copy option]

3. Follow the wizard and select the server to which you need to replicate the database to.

4. Save the changes, all the required folder and files will be created automatically similar to ver 2010 & 2013.

DAG - EAC - 6

 

DAG - EAC - 7

After the successful addition of database copy, you would be able to see that the database copy on server X1 status is Active Mounted and copy on X2 is Passive Healthy.

Creating the DAG and Adding members to DAG operations are much faster when you use Shell commands, however the through GUI it becomes easy to understand.

I will cover more operation on DBs and DAGs in future posts. Share your suggestions to improve the quality of information.

-Praveen

 

 

Published in Articles

Couple of times in the past, I observed this behavior that the database copy status turns to DisconnectedAndResynchronizing from DisconnectedAndHealthy after removing the activation restriction.

DisconnectedAndResynchronizing

This situation arise because, the copy try to replay the recent logs from other nodes. If your database copy could not find any copy to copy the pending logs, the status would stay the same for longer period.

Solution:

If you wish to have 2 DAG cluster with one of the cluster node as DR instance, then it is not a good idea to keep the ActivationSuspended parameter to true. Following are the approach you should consider to ensure a seamless recovery in case of a failover.

Option 1:

      1. Disable the ActivationSuspended value in the second node

      2. The database would failover immediately in the event of a node failure.

Option 2:

      1. Enable the ActivationSuspended value in the DR node

      2. In the event of active node failure, follow the DR procedure to evict the failed node prior to release the Activation suspension

It is recommended that, activation suspension can be released either when the nodes are available or after evicting failed nodes from the DAG cluster.

-Praveen

Published in Solutions
DAG (Database Availability Group) is the answer for Exchange 2010 database high availability. The Database Availability Group is a set of up to 16 exchange 2010 mailbox servers which gives automatic database-level recovery from a Database, Server or Network failures. If you are new to DAG concept see Database Availability Group.

In this blog we will see how to configure the Database Availability Group. We will be covering the following aspects,
  • Configure Databases
  • Create New DAG(Database Availability Group)
  • Add Mailbox Servers into DAG (Add members)
  • Managing DAG.
Published in Articles

Database Availability Group is the new cluster concept of Microsoft Exchange 2010. In other words DAG is the answer for Exchange 2010 database high availability. In this post I am trying to give you more insight about the Database Availability Group concept of Exchange 2010 and will try to clarify the queries as much as possible even though I know it is really not possible to cover every features of DAG in a post.

Before get into the feature of Database High Availability, let me tell you few more information about DAG. A Database Availability Group is a set of up to 16 exchange 2010 mailbox servers which gives automatic database-level recovery from a Database, Server or Network failures. DAGs are similar to Exchange 2007's SCR and CCR technologies, but mixed together, along with a few benefits.

  • Incremental Deployment:- You don't require to plan the numbers of server for DAG clustering, as an when you feel you can add more servers into DAG membership. This means if you want to deploy a DR server as a part of your production DAG it is all easy.
Published in Articles
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