In this blog we will be exploring some new feature introduced in Exchange Server 2013. Microsoft has introduced a new High Availability Feature “Automatic Reseed”. To simulate the scenario we have already created two member DAG.
Figure 1 : Two Node Dag
To understand the concept lets first explore the new DAG properties.
Figure 2 : Data properties
In figure 2 we can see some attributes as “AutoDag” with various options. The option available is the default option and there are some customization required to ensure that Automatic reseed works the way you expect.
Old Story – In Exchange Server 2010 if a disk fails then the entire database fails over from active node to passive node. And if the same happens in passive node then you might end up replacing the disk and start with either full reseed or manual reseed based on the database size.
New Story – In Exchange Server 2013 we have Automatic Reseed. So lets have a look at it how to configure the Automatic Reseed feature.
In figure 2 we have to set below properties as per our requirement.
- AutoDagDatabasesRootFolderPath : Default mount point for database.
- AutoDagDatabaseCopiesPerVolume : Allows us to set number of database copies per volume.
- AutoDagVolumesRootFolderPath : Default mount point for all volumes (Best practices is to have it in the root).
For more information on Best Practices on volume mount points please refer 280297.
Figure 3 : Folder Names Created in the root of C Drive.
In figure 3 Two folders are created for Volumes and Database.
Now first we have to create mount volume folders as shown below.
Figure 4 : Two directories for volumes
Now open disk management and we will create mount points using these two folders.
Figure 5 : Change Drive Letter and Paths
Figure 6 : Select Add
Figure 7 : Path
Figure 8 : Volume Mount Points Created
Figure 9 : Database Directory
Repeat steps 5,6 and 7 for database directory.
Figure 10 : Mount Volume for MDB1
Figure 11 : Comparing and Confirming Mount Volume.
Now lets create Data folder and Log File folder.
Figure 12 : Data folder and Log folder
In figure 12 when we create data folder and log folder. It must create the exact folders in E drive.
Figure 13 : Folders listed in E Drive.
Now Lets create database with the help of EMS.
Figure 14 : Create Database
Figure 15 : Created Successfully
After Creating the database mount the database. Post which add the database copy.
Figure 16 : Database Status
Lets test auto reseed.
Figure 17 : E Drive is offline.
In figure 17 E drive was taken offline forcefully to simulate the auto reseed functionality. In practical scenario it may be different.
Figure 18 : Status
Figure 19 : Auto reseed completed.
Note : To track the behavior in the background. You can refer the crimson log. Check “Seeding” on the source server where the drive has crashed. If the database is large it will take considerable amount of time to reseed.
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