pg_basebackup issues

Greetings,
I'm running postgresql-9.1.3 on a Linux-x86_64 (Fedora16, if it
matters) system. I noticed the existence of pg_basebackup starting in
9.1, and figured I'd try it out and see if it would simplify our
backup & management processes. I setup a test system (same OS &
postgresql version as production) with a fairly recent snapshot of our
production database, invoked it, and saw the following output:
######
# pg_basebackup -P -v -D backups -Ft -z -U postgres
135717206/135717230 kB (100%), 1/1 tablespace
pg_basebackup: could not get WAL end position from server
######

I wasn't sure what that error meant, so after googling a bit, turns
out that it really means that there were one or more files not owned
by the postgres user (see
http://serverfault.com/questions/312205/pg-basebackup-could-not-get-wal-end-position-from-server
). Sure enough, the file that wasn't owned by the postgres user was
the backup tarball that pg_basebackup was creating, since I had been
running it as root. That error is rather cryptic, and it would be
helpful if it was improved to suggest the real cause of the failure.
Anyway, lesson learned, I need to either invoke pg_basebackup as the
same user that runs the database (or is specified with the -U
parameter ?), or write the backup somewhere outside of the directory
structure that is being backed up.

I eventually also found the following entries in the postgresql server log:
FATAL: could not open directory "./backups": Permission denied
FATAL: archive member "backups/base.tar.gz" too large for tar format

What concerns me is the 2nd fatal error. The tarball that
pg_basebackup created before erroring out is about 12GB:
12393094165 base.tar.gz

I wasn't aware of any 12GB file size limit for tar, so this is a bit
of a mystery to me. Regardless, I'd be happy to try some other
archiving strategy, but the man page for pg_basebackup suggests that
there are only two formats, tar and basically just copying the
filesystem. If I copied the filesystem, I'd still have to find some
way to archive them for easy management (copying elsewhere, etc). Has
anyone come up with a good strategy on how to deal with it?

thanks