High availability refers to the accessibility of services at all time. This means that we can access the server at any time. However, that does not necessarily mean that if the server is up then it is available for services. A simple example would exemplify the scenario and that is when there is corruption of mailbox. Even though you are connected to Exchange Server, you are not able to access the mailbox database.
To ensure high availability in your organization, you can employ any of these techniques
Fault tolerance hard disk
Clustering
Third party tools
Virtualizations technology
Clustering In Exchange Server 2013 for Ensuring Availability of Services
Exchange server 2013 clustering is known as DAG and it is limited to 16 copies. Let us know then actual meaning of clustering. It allows you to incorporate a technology where you have multiple systems and incase of failover in the existing server; they are allowed to take the responsibility (continues to deliver services in case the active server mailbox role fails). This system would not make the users realize that there is any type of problem with server and hence the services would be available all time.
Creation of DAG in Exchange Server 2013
The following steps will show you the installation procedure of DAG in Exchange server 2013.The complete installation procedure can be divide into three main categories
Creation of computer object; DAG formation
Addition of members to the DAG group
Deploying DAG via Exchange Server Admin
Configuring database copies
Formation of Database Availability Group
Move to the domain controller and this can be done by executing the dsa.msc command on Run. It will lead to you Active directory and computers
Click on View and select the option Advance Features
Then create a new object of computer
It must be noted down that the name of the computer object must be same as that of DAG
Now you can find that DAG03 has been created. Next select properties
In DAG03, click object types and thick for computers:
Now, make the computer account for the DAG Full Control permissions
After that disable the DAG we have just created
Joining Members to DAG Group
The next step consists of adding members to the DAG that has been created.
Move to the file server or witness server. Type lusrmgr.msc on Run to open Local Users and Groups
Add the servers that you want to add the DAG and then click Save. This process will end with the addition of new DAG members to the cluster.
Deploying Exchange Server 2013 DAG
The last step consists of deploying an Exchange Server 2013 Database Availability Group. Follow the step given below to complete with the process of installation of DAG.
In the Exchange Admin Center carry out the settings given below
Give all the details like
DAG name
FQDN of the Witness server
Directory of the folder made on witness server
Provide an IP address to the DAG
Add the DAG members with the help of the + icon and save
Configuring the Database Copies
After that, the next step consists of configuring the copies of database. Follow the steps given below
In Exchange Console Panel move to servers – >databases tab
Select add database copy
Select the DAG member on which you want to add the database copy and then choose the server that will host the database copy from the list
To confirm that copy was successful move to DAG03 and you can find the creation of DAG on your hard drive
To check whether the installation procedure of DAG has been achieved successfully, you can carry out the following settings
In Exchange Control Panel
On the right side of the interface you will be able to see status for active and passive
Conclusion
The above content gives us an idea regarding the implementation of DAG in Exchange Server 2013. The concept of DAG has become very popular among organizations owing to its capability to restore service in the event of disaster.
Mark Jonathan Smith is a Tech. Blogger & he wrote posts on various topics related to Exchange Server & MS Outlook issues, conversion & migration. Mark is a MCITP certified & he continues focus on Active Directory, Exchange Server & Outlook.