Arnaud,

Before I answer this question, I would have to know the bandwidth of your
data link between the two sites.  The implementation would be different for
a slower link than a faster link.

Regardless, I've found that in every situation such as this, it is
beneficial to build two TSM server instances on each machine.  Server1 on
machine 1 and Server2 on the other machine 2 are the normally active
servers, and the others are placeholders in case you need to run both
servers on one machine during disaster recovery mode.

Once that is in place, virtual volumes for database backups will likely be
OK depending on the link speed and size of the database.  Because you know
that the opposite server will be running during a disaster, you can add
other functions as you add link speed.

Bill Smoldt
STORServer, Inc.