topic Re: Purpose of different tape device files in Operating System - HP-UX

Purpose of different tape device files

senthil_kumar_1 — Fri, 06 Jan 2012 12:51:09 GMT

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...

Re: Purpose of different tape device files

Torsten. — Fri, 06 Jan 2012 13:04:59 GMT

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

Re: Purpose of different tape device files

Patrick Wallek — Fri, 06 Jan 2012 16:49:46 GMT

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.

Re: Purpose of different tape device files

Bill Hassell — Sat, 07 Jan 2012 01:34:32 GMT

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.

Re: Purpose of different tape device files

senthil_kumar_1 — Thu, 12 Jan 2012 11:10:30 GMT

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?

Re: Purpose of different tape device files

Torsten. — Thu, 12 Jan 2012 11:30:14 GMT

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

Re: Purpose of different tape device files

Dennis Handly — Fri, 13 Jan 2012 00:24:11 GMT

>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.