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> To: "Simon J. Gerraty" <sjg@quick.com.au>
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> Subject: Re: kern/6434: compress/nocompress bit for tapes
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> On Fri, 13 Nov 1998, Simon J. Gerraty wrote:
> 
> : Just as there is a reserved bit in the tape device minor number to
> : control rewind/norewind, it would be very handy to have a bit that
> : controls whether compression is enabled or not.
> 
> What's wrong with "mt compress 1"/"mt compress 0"?

Nothing.  But it requires that everytime I feed a tape to Amanda
I need to run mt(1).  If /dev/nrst0c0 were a norewind,nocompress device
I could just configure Amanda to use that, and be sure that hw/
compression would not be used.

I agree that having a nocompress bit in the minor number might make 
"mt compress" less interesting, but that does not mean that a
nocompress bit is not the right thing.  Compression is the sort of
thing you turn on/off at the start of a mount session, so a minor bit
controll is quite applicable. 

In the interests of least surprise, it might be better to use two
bits in the minor number.

00 - nothing implied - use mt(1)
10 - compress off
11 - compress on

Thus /dev/nrst0 would continue to be have as it does.

--sjg