One of our clients was having an issue with backing up Exchange 2007 using Ahsay Online Backup Manager. The backups were failing nightly and Ahsay was returning the error CExBackup::backupService:HrESEBackupSetup: Error Number 0xc7fe1f45: Instance not found. A search of this error revealed that this error originated in Exchange and passed through to Ahsay. Checking the Application event log showed that for every failed backup there was an error with Event ID 904. The source is ESE Backup and the error text is Information Store (3396) Callback function call ErrESECBPrepareInstanceForBackup ended with error 0xC7FE1F45 Instance not found.
Researching this error online mostly pointed to this Microsoft Knowledge Base article, http://support.microsoft.com/kb/924204. However the article says this error occurs when the drive containing the transaction logs is full and I knew that this did not apply to the issue our client was having as they had nearly 245GB free on the drive where the transaction logs were stored.
I continued to search for answers and came across this posting from 2006; http://forums.msexchange.org/m_1800413118/mpage_1/key_/tm.htm#1800413118. In this forum thread the user Joseph Finnie reported that he observed this error when attempting to backup Exchange 2007 while a Recovery Storage Group was present on the server.
I checked the Exchange server for the presence of a RSG by opening the Exchange Management Console, selecting Toolbox and then selecting Database Recovery Management. This opens the Microsoft Exchange Troubleshooting Assistant. After the TA connects to Active Directory you will come to a page that says “Select one of the following tasks” and the section you want to look under is “Manage Recovery Storage Group.” If there is an RSG present, click the link for “Remove recovery storage group.” Once the RSG was removed this error stopped occurring and the backups completed successfully.