Storage management?????

Scalability -

I'm new to Postgres and I am noticing there are no commands to create files
or tablespaces and manage storage of data over several disks for either
table partitioning or seperating tables and indexes. How do you manage
scalability of the database and strategic placement of objects or files
over several disks? I don't fully understand how the database is stored
and how it extends when it needs to. How do you impose size limits and how
do can you store and manage, for example, a 100Gig database?

Backup/Monitoring -

How do you backup and recover using WAL transaction logging to roll forward
a database to the point in time of failure?
Does anyone have a comprehensive set of backup/recovery and database
monitoring scripts they can send my way for both data wharehousing and
transactional database so I don't have to re-invent the wheel? Or are
there any scripts published or available for download anywhere?

pg_dumpall errors -

I am using postgres user with same password in all the databases but still
the pg_dumpall program tries to interactively authenticate even though I am
using "local trust" in pg_hba.config. Any suggestions?