[DRBD-user] Intro questions

[Alex]

Hi,

I posted this message a few days ago and I'm not sure it was received.
I'm really hoping someone can help.

I'm trying to understand how drbd works and how all the different
pieces go together. I first installed drbd on Linux many, many years
ago, but it appears to be quite different and obviously more mature.

I have a mail server with about 3TB of disk space for users. I'd like
to create a completely different system on a completely different
network and somehow provide a single interface for users to access
their email.

Does drbd typically work with a front-end system that helps to manage
which system is active?

Ideally I'd like a system where I can advertise a single IP address in
DNS and have traffic routed to the currently active system but I don't
really understand how all the pieces go together.

Does drbd typically involve NFS? LVM?

Is there a general overview doc that provides a description of typical
configurations?

What are the services that are available as open source as compared
with the ones offered commercially by linbit?

Thanks,
Alex