I can't specifically address the silos issue, but, I would highly recommend
you check out the licensing issues with Legato NetWorker.  If you buy GEMS,
or spend a million bucks on a enterprise license, this is not an issue.  But
if you plan on deploying Legato on a large scale, Legato's licensing is a
pain to administer.  They base their authorization codes on hardware config,
IP address, HOST name, an who knows what else.  Any changes in these
configuration parameters on your NetWorker server, will invalidate your
license on that server.

Good luck!  Feel free to contact me at gsheis AT fedex DOT com for details.

Greg Heis