On 4 Jun 2000, Eric Smith wrote:

> > does it work if you remove the z option in tar. I have experience some
> > problems with my dds2 and dds3 when trying to apply gnuzip to the tar
> > archive. I have a ultrix with a tk50 i can do some research in this area
> > later and tell how it reacts to the option z in tar.
> 
> I'm not disputing that there might be a problem, since I haven't tried
> it myself, but the very concept that a TK50 might have problems with
> the gnutar -z option amazes me.  How would the TK50 even "know"?

Let me put it this way: It's not about TK50 knowing about the -z option,
it's about gzip not knowing about tapes...
Unix by default act like an idiot when we talk tapes. tar *knows* about
tapes, and can handle them much better. However, if you add the -z option,
tar knows it's talking to a pipe instead, so you loose tar's tape
handling. Instead you get the data to gzip, and gzip is a stupid program.

I would say that by using the -z option, you will actually get less data
into the tape than if you run uncompressed data.
This has to do with block size and inter-records gaps. If anyone want to,
we can go deeper into this story, otherwise: just trust me. :-)

Simply put: don't use -z when writing to tapes.

	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