Managing Space in PostgreSQL - DBA Perspective

I'm evaluating PostgreSQL as an alternative to Oracle and the more I look at
PostgreSQL the more I like it!!!

From a DBA perspective, how easy is space management? For instance... In
PostgreSQL I can't correlate the data files to specific tablespaces by a
naming convention. How easy is it to move things around without taking the
database down? How easy is it to segregate I/O contending database objects
like tables and indexes? Log files? Etc? How easy is it to preallocate
space? Is it possible to take a subset of tables/indexes offline and keep
the database up? Are there any other PostgreSQL space management challenges
or gotchas that I have yet to discover?

I'm in the process of trying to answer many of these questions myself but
I'm under a time crunch so I was wondering if anyone on this list could have
compassion on this newbie and help me out. :-)


Many thanks in advance,
Steve Orr