Testing, Testing, 1, 2, 3...
Disaster recovery plans should be part of any testing plan.
I do my research and testing within the confines of a test network. Sometimes
it's a single Windows forest with a single domain and sometimes it's a
multi-domain, multi-forest, multi-OS monster. Mostly it's not meant to
exist for more than a few months, so I don't spend a lot of time worrying
about keeping it viable in the face of natural disaster or even simple
hard drive failure. If something in the test Windows network dies, it's
not going to mean its not going to put me out of business. Can you say
Do you have a disaster recovery plan for your Windows network? I'm not
talking about simple data or even system backup here. I'm talking about
your plan for completely recovering from the loss of your Active Directory
infrastructure. Could you withstand the loss of one of your operations
masters? How about the first domain controller installed in a domain?
How long would it take to rebuild the DC? Would that time span be short
enough to prevent you from major revenue loss?
There are two themes here: First, you should have a comprehensive plan
for recovering from the loss of any part of, or all of, your AD infrastructure.
Second, you should be able to do so without causing your business financial
First things first. What should you be doing today that might save your
hide tomorrow? Here are three important steps: if you aren't doing them,
you should be asking yourself why.
- Back up every DC, but make doubly sure you back up every operations
role master, global catalog server and the first DC in the domain. You
can only restore a DC from its own backup. You can create new DCs in
the domain to take the place of those that serve no special role, and
you can recover operation masters and rebuild a GC, but can you do so
- Back up frequently. A backup older than the tombstone age set in
AD is not a backup. A tombstone represents a deleted item. The tombstone
exists so that an item can be replicated throughout AD, making sure
that each DC eventually has deleted the item. If your backup is older
than the tombstone age, you won't be able to successfully use it to
restore a healthy AD back to your pre-disaster state.
- Practice recovery of each type of DC loss. If you don't have a test
network to attempt this on, get one. It's a small investment that can
There's a lot more to disaster recovery—and, more importantly, maintaining
business continuity. If you've got some statistics on the time it took
you to recover from an AD failure, let me know.
Roberta Bragg, MCSE: Security, CISSP, Security+, and Microsoft MVP is a Redmond contributing editor and the owner of Have Computer Will Travel Inc., an independent firm specializing in information security and operating systems. She's series editor for Osborne/McGraw-Hill's Hardening series, books that instruct you on how to secure your networks before you are hacked, and author of the first book in the series, Hardening Windows Systems.