Dial-tone revisited

The theory of Dial-Tone Recovery (DTR) is one that has often been overlooked in the world of Disaster Recovery (DR) for Exchange Server.  However, even in Exchange 2007, DTR can provide a great method for immediate restoration of email services, though with a few things to keep in mind.

For those who haven't heard of DTR before, here's a primer:

If a primary Exchange 2000, 2003 or 2007 server fails, you can attempt to restore services by deleting the corrupted databases and re-starting Exchange services.  This will create blank databases and allow users to send and receive new mail, access new calendar items and access all shared contact information.  Running a /disasterrecovery install of Exchange on a rebuilt box with no data will do the same thing.  Though end-users can access their email systems again, there will be no historical data, so this isn't a total solution set for true DR, but gives you some options for immediate availability.

In an emergency, this can give you time to perform restoration steps - which could take quite a while to finish - without making everyone wait to get back basic send/receive capability. You can restore a copy of the historical data via several methods, taking the time you need to do it right.

If you used a brick-level tape or disk backup solution, you can restore mailboxes via that tool's recovery system. Archiving solutions and Continuous Data Recovery systems (like TimeData from Double-Take - see disclaimer below), can let you move mailbox, folder and other data back over time as well.  If neither of those tools are at your disposal, but you to have a backup of the database and logs, you can restore those to a Recovery Storage Group, and use ExMerge or Exchange 2007 tools to bring back mailbox data and merge it with the new information on the DTR-recovered server.

If no backup is available at all, you can still provide Exchange services from the point of DTR onward.  While no historical info will be available to them, the end-users will be able to send and receive new email, calendar entries and Public Folder data.