TAR DOES NOT SWAP BYTES (3B20 tape block size)

[Arnold Robbins]

In article <578 at im4u.UUCP>, jsq at im4u.UUCP (John Quarterman) writes:
> >I think the problem is with the 3B20 tape drive, not with "tar" on the 3B20.
> >Some tape controller (which I think they've junked in favor of a sane one)
> >imposes a rather small minimum block size; "tar cb 20 ..." exceeds this
> >limit.
> 
> The limit is 10, and you also have to specify the blocksize manually
> when extracting a tape, as well as when writing one.
> -- 
> John Quarterman

The actual limit for blocks that can be written to and read from the tape
drive on the 3B20 is 6K (using the raw device).  I found this out when porting
a really neat backup program to our two 3B20s. So Jsq's comment is correct,
a tar block size of 10 is 5K bytes (tar's "block" is 512 bytes).

This limit really sucks.  Whoever made that decision at AT&T must not have
been someone who actually had to move tapes around.  When is AT&T going
to take their heads out of the sand? The 3B20s are hardware to run UNIX
on, not the other way around!!!
-- 
Arnold Robbins
CSNET:	arnold at gatech	ARPA:	arnold%gatech.csnet at csnet-relay.arpa
UUCP:	{ akgua, allegra, hplabs, ihnp4, seismo, ut-sally }!gatech!arnold

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