On 26 Oct 1998, Tom Ivar Helbekkmo wrote:

> allisonp@world.std.com (Allison J Parent) writes:
> 
> > Officially 95mb.  depending on how you structure your data and all it 
> > could be as low as 60mb usable. I used to use it to completley image 
> > backup RD53s (71mb) with room to spare.  20mb is way out of line.
> 
> I've been doing 'dump -b 32 -B 90000' here lately.  That is, 32KB
> records and 90000KB expected to fit on the tape.  This was after a
> 'dd bs=32k' that errored out after 92000KB.  On the other, hand, a
> test with 'dd bs=256kb' the other day bombed out after 88832KB; I
> don't know what to think of this.  Aren't all TK50s the same?

Interesting. First of all, all TK50 aren't *exactly* the same size,
obviously it would be pretty hard to really measure things up that
precise.

Secondly, I wonder what dd thinks when you say 'bs=256kb', is it 256
kilobytes, or 256 blocks (of 512 bytes).

> Anyway, as Allison says, it depends on your record size.  Do a test
> run over a couple of tapes (if you want to use tar, use 'dd bs=10k')
> and see what happens.

One important thing, no matter what, is that larger block size means fewer
inter-gap records, which is a "waste" of tape. Large blocks however, also
means you might loose at the end of files, if the program don't pack
things intelligently.

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt@update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol