Exchange For high availability, the server must be configured in the Exchange Server's Database Availability Group (DAY) feature provides redundancy between servers and thus prevents service interruptions. In this context, DAG's AutoReseed feature comes to the fore. AutoReseed is defined as a feature that automatically replaces the faulty disk with a spare disk in the event of a disk failure and quickly makes this spare disk available for the database.
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With Exchange Server DAG, if you lose the disk where your database is located (active or passive), Exchange will failover that database to another server (assuming it is part of a DAG with multiple copies).
The purpose of AutoReseed is to overcome this situation and provide database redundancy by using specially provided backup disks. All it does is pre-map the volumes and databases using the mount points that will be used for databases and reseeding. Simply:
- Mount the entire disk (used for databases and as backup) under a single mount point, for example C:ExchangeVolumes;
- The root directory of the mailbox databases, for example C:ExchangeDatabases mount it as another mount point under . Next, create two directories for each database: one for the database itself, and one for the log files;
- Finally, create the databases.
The diagram below should help understand this design, but it will become clearer once we go through all the steps.
First, let's look at the AutoReseed process flow:
- Exchange Replication service, status FailedAndSuspended scans database copies at regular intervals;
- If one is found, it performs prerequisite checks such as checking that replacement drives are available and ensuring that nothing can prevent Exchange from automatically reseeding the database;
- If all checks pass, the Replication service allocates a spare drive and remaps it;
- The seeding process is done;
- After the separation process is complete, the Replication service checks whether the seed copy is healthy.

The workflow starts with the detection of the failed volume. Database copies are updated whenever any of them have been down for 15 minutes or more.FailedAndSuspended" is checked regularly to see if it is in a " state. This is the state the database copy will be in if there is an underlying storage issue. The 15 minute threshold is there to ensure that corrective action is not taken too quickly.
Working Principle of AutoReseed
Within a DAG, each database can typically reside on more than one server. If one server goes down, Exchange Server automatically starts using the copy on another server. This process is usually automatic, and most users won't notice the change. (A healthy DAG makes the active-passive transition in a maximum of 30 seconds)
However, in the event of a disk failure, the database copy on the disk may be deleted. In this case, AutoReseed process is activated. AutoReseed, replaces the failed disk with a spare disk and automatically uses this disk for the database. Then, the database copy on the failed disk is re-created on this new disk.seed” is made, that is, copied.
Advantages of AutoReseed
- Automatic: AutoReseedInstead of manually performing database copy operations in case of disk failures, it does this automatically.
- Continuity: AutoReseed, ensures service continuity. If a disk failure occurs, AutoReseed Thanks to this, operations continue without interruption.
- Flexible Management: AutoReseed feature, Exchange Admin Center or Exchange Management Shell It can be easily configured and managed through Exchange Server configuration and management tools such as.
Disadvantages and Limitations of AutoReseed
- Additional Disk Requirement: AutoReseedrequires an additional backup disk for each database. This requires more disk capacity, which can increase costs.
- Configuration Complexity: AutoReseedIn order for to function properly, disks and databases must be configured in a specific order. This can be complex and require expert knowledge in large-scale Exchange Server configurations.
- Limited Fault Tolerance: AutoReseed, can only handle disk-level errors. If a server crashes or network errors occur, AutoReseed cannot manage such situations. Therefore, AutoReseedA comprehensive fault tolerance and disaster protection strategy should be in place as part of the
Conclusion
AutoReseed, Exchange ServerIt is an important feature of , especially large and complex Exchange Server It is important to ensure service continuity in their configurations. However, to use this feature most effectively, Exchange Server managers need to understand this feature and its working principles well and apply it appropriately. This article, AutoReseedIt aims to fill the knowledge gap in this field by addressing the basic working principles, advantages and disadvantages of .
As you see Autoreseed It is quite smart and efficient, it can fix a simple problem like storage failure without any manual intervention by the administrator other than replacing the failed disk with a new spare.
Autoreseed every time DAYIt can successfully restore the durability of my . Looking at the event logs it usually does this in a little over an hour. (May vary depending on DB size)
Autoreseedis a feature of a highly intelligent server application designed to operate efficiently at scale.