Is there a concept of Redo log files in postgres.?

Hi,

I wanted to know like in oracle there is a concept of redo log files meant for backup and recovery. Is the same concept
presentin postgres.I have gone thru the documentation .it says backup can be taken thru 2 approaches 
    1.SQL Dump
    2.File System level backup.

for SQL Dump command is      ----> pg_dump dbname > outfile
for file system level backup ----> tar -cf backup.tar /usr/local/pgsql/data.


the second method is not practical cos we need to shut down the database server to make use of the tar.

Is there any other method's to back up data and restore data incase of media failure.?

thanks in advance

Somasekhar Bangalore