The Microsoft Exchange Replication Service was unable to perform an incremental re-seed of the passive node for the clustered mailbox server ‘%1’ because the log files on the active node have diverged too widely from the log files on the passive node. A full re-seed of the passive node for this storage group is required. Re-seeding can be done by using the Update-StorageGroupCopy cmdlet in the Exchange Management Shell.

Details
Product: Exchange
Event ID: 2056
Source: MSExchangeRepl
Version: 8.0
Symbolic Name: ReseedRequired
Message: The Microsoft Exchange Replication Service was unable to perform an incremental re-seed of the passive node for the clustered mailbox server ‘%1’ because the log files on the active node have diverged too widely from the log files on the passive node. A full re-seed of the passive node for this storage group is required. Re-seeding can be done by using the Update-StorageGroupCopy cmdlet in the Exchange Management Shell.
   
Explanation

This Error event indicates that the Microsoft® Exchange Replication (MSExchangeRepl) service could not perform an incremental reseed of the passive node because the logs on the active node have diverged too widely from the logs on the passive node.

Incremental reseed must see the active log stream in order to perform its operation.

The Microsoft Exchange Replication service tries to perform an incremental reseed after a failover if the passive and active database copies for the specified storage group are out of sync. An incremental reseed is performed to avoid a full reseed. The replication service detects that the copy of the database on the active node has diverged from the copy on passive node when the passive node is restored. The replication service then tries to resynchronize with the now active database.

Note   Incremental reseed cannot detect log file divergence until there is traffic to the storage group.

The event will only appear when the passive node returns to service after it has been previously active and then failed. Generally, there are three conditions can cause the database copy on the passive node to diverge:

  • The active database was manually mounted after the failover because it was outside the auto-mount criteria but is still an acceptable version of the data. This would have to be explicitly done by the administrator. Such actions guarantee a reseed.

  • The system experienced a split brain condition because of a software error or operator error.

    Note   The Microsoft Cluster Services (MSCS) can usually avoid this condition. However, in rare cases, you can have this condition when both nodes think they are active and generate their own set of logs independently. Therefore, logs of the same name on each node will contain different content.

  • The failure occurred when the active node could continue for a brief period although it was not outwardly available. This can occur when there are concurrent double failures on the networks and all traffic to the active node is prevented. MSCS lets the mailbox server run while MSCS determines whether it can re-form quorum. At the same time, the passive node may be able to form quorum and bring the mailbox server and its databases online. This is a short window of about 30 seconds. The probability that this condition will occur is reduced if the cluster group owner is the same as clustered mailbox server owner.

    Note   During this time clients cannot be served. Therefore any traffic that is committed must be maintenance activity.

For more information about CCR, see Cluster Continuous Replication.

   
User Action

To resolve the error, reseed the storage group copy on the passive node. Follow the steps outlined in this topic, How to Seed a Cluster Continuous Replication Copy.

If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.

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