ioctl for DAT compression

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2 total messages Started by Mike Matthews Fri, 21 Aug 1992 12:36

#991

Author: Mike Matthews
Date: Fri, 21 Aug 1992 12:36

18 lines
1110 bytes

Does anyone know the ioctl or whatever to turn hardware compression ON on an
Eclipse 4mm DAT tape drive?

I know that RunningBack has the option but it's manual is actually quite
worse than anything NeXT put out (well, the manual that I've seen at least)
and doesn't say anything other than how to plug it in.

Also, is there a way to determine if a tape is in the drive and ready to go?
I tried mt -f /dev/nrst0 status but it never gave consistent errors (returned
06, then 02, then 00 without me doing anything  -- and this was after the
ready light came back on too).
------
Mike Matthews, matthews@oberon.umd.edu (NeXTmail accepted)
------
If A equals success, then the formula is:
   A= X + Y + Z
X is work. Y is play. Z is keep your mouth shut.
- Albert Einstein

Re: ioctl for DAT compression

#994

Author: Sherwood Botsford
Date: Fri, 21 Aug 1992 18:31

38 lines
1699 bytes

Mike Matthews writes
> 
> Also, is there a way to determine if a tape is in the  
drive and ready to go?
> I tried mt -f /dev/nrst0 status but it never gave  
consistent errors (returned
> 06, then 02, then 00 without me doing anything  -- and  
this was after the
> ready light came back on too).

6 means that the device has been reset or there has been a  
change of cartridge.

2 means that the device is not ready.

0 means everything is ok.

80 means that there is a tape loaded, and its at a  
filemark.

40 means that there is a tape loaded and its at Logical  
Beginning of tape.

Status remains set until the drive receives a command.   
Thus you could have changed the tape 10 minutes ago, and mt  
status will return 6.

Get TarChive.tar.Z if you want to see some samples of how  
to check status and decide what to do from there. (On  
sonata.)

I think you could modify the mtsense command in that same  
file to set compression on.

CAVEAT:  Using compression on a Tape drive is not a good  
plan.  If you have a glitch, the remainder of the  
compressed archive is usually undecipherable.  Don't do  
this unless you can't fit what you want on a single tape.

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