Splitting tar output

[Jim Kuzdrall]

Greetings,

    Does anyone know how to create a tar tape archive and disk file 
archive at the same time?

    The present system does something like:
cd /
tar -cf $bkdir/monthly.tar ./ $bkoptions
tar -cf /dev/st0 ./ $bkoptions

    It takes an appreciable time to read and write 8GB to disk in the 
first tar call.  The tape operation which follows is even slower.  If I 
could get the first tar output piped into the tape, the whole operation 
would take the same time as the second tar call, the disk writing being 
done while waiting for the tape.

    I have tried tee, cpio, dd, and various pipes to no avail.  I am 
beginning to suspect that the bit stream tar produces to write to tape 
is not the same as that it writes to disk.  Could that be so?  

    I can get the entire archive back if I put it on with some cpio or 
dd schemes, but tar won't list or extract files directly from the tape.

    One alternative is to run the disk archiving simultaneously as a 
background task.

    Any better ideas?

Jim Kuzdrall