Why isn't dump maximally efficient with TK70 tapes?

[George Robbins]

In article <1990Jun8.014252.15749 at watcgl.waterloo.edu> idallen at watcgl.waterloo.edu (Ian! D. Allen [CGL]) writes:

>       DUMP: This dump will occupy 1103 (10240 byte) blocks on 0.13 tape(s).
					  
>     recorder# time sh -c "dump 0f - / | dd bs=32k rbuf=2 wbuf=2 of=/dev/rmt0h"
						^
> That's almost three times faster!  Why can't dump be as good as dd?
		
> Dumps are of major importance; I would have thought that dump would be
> the most clever user of the tape drive.  I can't believe this.  Am I
> missing something?  I must be missing something.

Mostly that dump doesn't document the -b switch to let you specify a more
efficient block size and restore doesn't support it, which makes it a
pain to restore tapes with non-standard block sizes.
-- 
George Robbins - now working for,     uucp:   {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing:   domain: grr at cbmvax.commodore.com
Commodore, Engineering Department     phone:  215-431-9349 (only by moonlite)