%1 (%2) %3The log signature of the existing logfile %4 doesn’t match the logfiles from the backup set. Logfile replay cannot succeed unless all signatures match.

This Warning event indicates that the log signature of an existing log file does not match the log files from the backup set. You are restoring to a recovery server that has a different set of log files. Log file replay cannot succeed unless all signatures match.

You will see the following phrase in the event description: Information Store number. The log signature of the existing log file E0n.log does not match the log files from the backup set. Log file replay cannot succeed unless all signatures match.

The E0n.log file (the current log file for the storage group, such as E00.log) has a different log signature than the log files that have been restored from the online restore. A typical scenario is as follows: All the Microsoft Exchange Information Store service files have been removed. In order to restore an online backup of an Exchange server, you must have the Exchange store running. If you have not checked the Do not mount this store at start-up option on the Database tab, and you start the Microsoft Exchange Information Store service, then a new E00.log file is created. The log signature for this file does not match the signatures of the log files from the backup, and the Exchange store fails to replay logs and mount the databases.

To resolve this warning, do the following:

1. Disconnect from all the databases in the storage group.

2. Perform an offline backup and then remove all Exchange store log files and check files for the storage group. Select the Do not mount this store at start-up option on the Database tab for all databases in the storage group.

3. Start the Microsoft Exchange Information Store service. Clear the Do not mount this store at start-up option on the Database tab for all databases in the storage group. Perform the online restore.

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.