online tape backup

Hi:

I'm attempting to set up online backup as described on
http://www.postgresql.org/docs/8.1/static/backup-online.html
For this, i am following these steps:

1) pg_start_backup
2) tar to my tape device /data/postgresql excluding /data/postgresql/pg_xlog
3) pg_stop_backup
4) delete WAL files under /data/pg_trans_log/ (which is the directory to which
archive_command copies my archived WAL files) with name "smaller" than the
name of the last 000*.backup
5) append to previously created tar on the tape the WAL
directory /data/pg_trans_log/

So, you see, i run tar 2 times, first for pg data dir, second for wal archive
dir. Everything worked OK for about a week. Now the second tar (the one
archiving the WAL files) exits with status 2, no errors on stderr. If i
check the contents of the tar on the tape, they are wrong.

Is there anything wrong with this procedure? Any other approaches to tape
backup that do *not* involve using pg_dump (because of database size, dump
time and performance issues)?

Any help is greatly appreciated.

--
Eduardo J. Ortega - Linux user #222873
"No fake - I'm a big fan of konqueror, and I use it for everything." -- Linus
Torvalds