- a single OMERO master started with `bin/omero admin start`
- optionally a second OMERO node started with `bin/omero node start`
- two Blitz services defined in `etc/grid/default.xml`, both of which stay online as long as they have active sessions
- a single view of PostgreSQL from the 2 Blitz services (i.e. via ssbd3)
And with respect to the UUIDs, it shouldn't matter how you have OMERO.web, Apache, nor PostgreSQL load-balanced, though PostgreSQL will always have to be available.
Cheers,
~Josh