How do I prepare my DR NT Domain for Exchange Recovery

Exchange 5.5 Disaster Recovery on NT4


N.B. as the title says this guide only covers Exchange 5.5 on NT4. I have no details on the recovery required for Windows 2000, nor any experience of recovering Exchange 2000 yet.

In order to recover your Exchange server the NT SAM at your DR site must match that of your production site.

The first and probably most important point is obviously you must have a recoverable backup of Exchange and just as importantly a copy of the %systemroot%\system32\config directory from your PDC or one of your BDCs.

When you build your new PDC at the DR site it will create a new SAM with it's own security, users etc. Since NT has these files locked from startup you can't simply overwrite them with your restore, you should use a bootable DOS disk to get around this.

In order to use the DOS floppy though, you have to format the system partition on the PDC as a FAT partition. If this isn't done you won't be able to access the drive using DOS.

Having fully built the PDC we then create two directories on the system partition, eg c:\safereg and c:\custreg.

Restore the production %systemroot%\system32\config directory from your tape to the custreg directory.

Restart the PDC using the bootable DOS floppy.

Copy %systemroot%\system32\config to the safereg directory. This gives you a backout option if you have problems with your restored files.

Copy the SAM and SECURITY files from the custreg directory to %systemroot%\system32\config. Overwrite the existing files. This step should bring your production environment over without affecting the hardware and software registry hives.

Restart the machine to NT. You should find when opening User Manager for Domains that your production user logins are there rather than the Administrator and Guest that the NT installation created when you built the new PDC.

With the correct SAM in place you should be able to restore Exchange, by whichever method you normally use, to the chosen server.

The last few points to make here are with regard to testing. Firstly test your backups, there's no point getting to the DR site and finding you can't read your tapes. Secondly test this procedure. Get familiar with it. It has worked for me on at least half a dozen occasions now (DR tests and setting up/updating our in-house test network), though I've never had to use it for real!

Finally be prepared for things to go wrong in a big way. The last time we did a DR test, the DLT drives that our DR company used jammed 2 of my tapes and wouldn't eject. I had to get my on-site copy delivered by taxi in order to get the above procedure started!


Hope this helps all of you who have to test your recovery, even more so anyone unfortunate enough to have to do the real thing.



If anyone sees any glaring errors in here, please let me know.

David Cain
Information Systems
Britannic Asset Management