backup archive format saved to disk

[Douglas Tutty <dtutty@porchlight.ca>]

Hello,

I'm going to be backing up to a portable ruggedized hard drive.
Currently, my backups end up in tar.bz2 format.

It would be nice if there was some redundancy in the data stream to
handle blocks that go bad while the drive is in storage (e.g. archive).

How is this handled on tape?  Is it built-into the hardware
compression?

Do I need to put a file system on a disk partition if I'm only saving
one archive file or can I just write the archive to the partition
directly (and read it back) as if it was a scsi tape?

Is there an archive or compression format that includes the ability to
not only detect errors but to correct them? (e.g. store ECC data
elsewhere in the file)  If there was, and I could write it directly to
the disk, then that would solve the blocks-failing-while-drive-stored
issue.

Thanks,

Doug.