Hello Col-

I just wanted to expand on Milind's excellent response a bit.

I'd recommend separating your requirements for disaster recovery and
remote document access. Here is a proposal:

1. Designate one of your offices as the primary data center (if the
user populations are similar, then select the site with the best IT
support).

2. Establish the centralized repository at that location. Build it on
top of a robust SQL server and a speedy SAN. Make sure bandwidth is
not a bottleneck. Follow normal data back-up procedures to protect
against data corruption -- nothing worse than a perfectly-replicated
corrupted database.

3. Create a disaster recovery (DR) data center in that same locality.
Make sure that it's far enough away to avoid common-mode disasters but
close enough so that you can still lease data lines between the two
facilities. Duplicate the hardware found in the primary data center.

4. Establish your near real-time replication between the primary data
center and the DR data center.

5. Bring up the secondary office with the caching server as described.
Use DNS to point the caching server and users local to the primary
data center to your centralized repository.

6. In the event of a disaster or server failure at the primary data
center, simply update the DNS to point to the DR data center.

7. Run periodic DR drills to verify your replication and your
procedures.

Hope that helps

-John