I'm trying to use pv (pipeviewer) along with tar to do tape backups in order to see the progress and eta like so:

du -s /home/myuser

115630916   /home/myuser

tar -cf - /home/myuser/ | pv -s 115630916 > /dev/nst0

Which works fine, it writes to tape successfully. But once I try and test the tar archive:

mt -f /dev/nst0 rewind

tar -tvf /dev/nst0

I get the following errors:

tar: /dev/nst0: Cannot read: Cannot allocate memory

tar: At beginning of tape, quitting now

tar: Error is not recoverable: exiting

I've googled around and there have been suggestions that I use --blocking-factor=128 when creating my backup and restoring. I still get the same error.

It's also worth noting that if I just use tar, everything works 100%, including the restore, so perhaps pv is breaking it?