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Purpose of different tape device files

senthil_kumar_1
Super Advisor

Purpose of different tape device files

Hi All,

 

I am seeing 8 device files for single tape drive in HPUX...

 

#ioscan -funC tape
Class     I  H/W Path     Driver S/W State   H/W Type     Description
=====================================================================
tape      0  0/5/2/0.1.0  stape CLAIMED     DEVICE       HP      Ultrium 1-SCSI
                         /dev/rmt/0m            /dev/rmt/0mn           /dev/rmt/c4t1d0BEST    /dev/rmt/c4t1d0BESTn
                         /dev/rmt/0mb           /dev/rmt/0mnb          /dev/rmt/c4t1d0BESTb   /dev/rmt/c4t1d0BESTnb

 

 

Could you please explain the purpose of each one and which one is default and which we have to use for better result...

6 REPLIES
Torsten.
Acclaimed Contributor

Re: Purpose of different tape device files

BEST is best density possible (same as 0m); BESTb is Berkeley style; "n" always means "no rewind".

 

For AT&T vs. Berkeley see http://h30499.www3.hp.com/t5/General/Tape-AT-amp-T-and-Berkeley-style/td-p/4472927


Hope this helps!
Regards
Torsten.

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Patrick Wallek
Honored Contributor

Re: Purpose of different tape device files

The '0m' names (0m, 0mn, 0mb, 0mnb) are alternate names for the c4t1d0BEST names (c4t1d0BEST = 0m, c4t1d0BESTn = 0mn, etc.).

 

Torsten has already given a good explanation of the *m,mn,mb,mnb names.

Bill Hassell
Honored Contributor

Re: Purpose of different tape device files

There is a special command to decode the device files: lssf

 

     lssf /dev/rmt/*

 

The various device files are used to set specific behaviors for the tape drive such as rewind after close, compression on or off, etc. These device files are used with programs that do not provide methods to handle these features. tar is an example. Although it is called tape file archive, it has no controls for tape drive, so these device files take care of the desired behavior.



Bill Hassell, sysadmin
senthil_kumar_1
Super Advisor

Re: Purpose of different tape device files

Hi All,

Thanks a lot for your informations...

What is difference between re-wind and no-rewind?

Which option is best and why and where?
Torsten.
Acclaimed Contributor

Re: Purpose of different tape device files

After a write the drive rewinds the tape back to the beginning, a "no-rewind" does not rewind the tape after write.

Hope this helps!
Regards
Torsten.

__________________________________________________
There are only 10 types of people in the world -
those who understand binary, and those who don't.

__________________________________________________
No support by private messages. Please ask the forum!

If you feel this was helpful please click the KUDOS! thumb below!   
Dennis Handly
Acclaimed Contributor

Re: Purpose of different tape device files

>Which option is best and why and where?

 

I depends.  If you want to append to the tape, you need norewind.

You also need it to use mt(1) to space forward, otherwise, it is rewound after mt(1) closes the file.