🚀 go-pugleaf

In <1992Jul26.115817.27702@mic.ucla.edu> iwelch@agsm.ucla.edu (Ivo Welch) writes:
| I would like to write a few programs to lay out our large databases onto a DAT
| tape.  Unfortunately,  I  lack all expertise with   tape  drives,  and my Wang
| manual is less than explicit.
| 
| I understand how to use devices (/dev/rxt0, /dev/nrxt0) to read and write data
| byte by byte and  file by  file.  What I   really  would like, though, is  the
| additional ability to  keep an  index on   disk,  and do a  fast fseek()  that
| employs the WangDATs fast seek facilities. How would I do this in a C program?
| 
| I.e. could some kind sole please send me replacements  for fseek() and ftell()
| with such DAT tape drives, please?

The drive has the ability to do fast seeks, but fseek and ftell are
unlikely to work.  It may also be that the NeXT tape drive doesn't
provide this functionality.
--
Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com

In article <nq9sp2o@zuni.esd.sgi.com> olson@anchor.esd.sgi.com (Dave Olson) writes:
>In <1992Jul26.115817.27702@mic.ucla.edu> iwelch@agsm.ucla.edu (Ivo Welch) writes:
>| I would like to write a few programs to lay out our large databases onto a DAT
>| tape.  Unfortunately,  I  lack all expertise with   tape  drives,  and my Wang
>| manual is less than explicit.
>| 
>| I understand how to use devices (/dev/rxt0, /dev/nrxt0) to read and write data
>| byte by byte and  file by  file.  What I   really  would like, though, is  the
>| additional ability to  keep an  index on   disk,  and do a  fast fseek()  that
>| employs the WangDATs fast seek facilities. How would I do this in a C program?
>| 
>| I.e. could some kind sole please send me replacements  for fseek() and ftell()
>| with such DAT tape drives, please?
>
>The drive has the ability to do fast seeks, but fseek and ftell are
>unlikely to work.  It may also be that the NeXT tape drive doesn't
>provide this functionality.

There is no "built-in" support for random seeking to blocks on DAT
tape media, but it is not too difficult to issue "raw" SCSI commands
to the tape driver with the appropriate commands to perform the
seeking.  

Seeking is the easy part; maintaining the database of where to seek
*to* is the tough part.  This is one of the features of the Safetynet
program mentioned in the original article.

louie

> There is no "built-in" support for random seeking to blocks on DAT
> tape media, but it is not too difficult to issue "raw" SCSI commands
> to the tape driver with the appropriate commands to perform the
> seeking.  

Yes, but the question remains: WHAT ARE THE COMMANDS TO DO SO FOR WANGDATS?

(I got 4 messages asking me to forward any responses; unfortunately I have not
received any). Again, has anybody written C functions that can substitute for
fseek() and ftell() (probably over the whole tape, rather than a file, which
would be just fine).

I can no longer get a hold of the author of Safteynet, nor will Safetynet do
what I need: maintaining data-bases to be read by programs. I do not primarily
want to increase dump/tar/etc speed!!

/ivo welch
Newsgroups: comp.sys.next.sysadmin
Subject: Re: WangDAT: How to fseek() ?
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References: <1992Jul26.115817.27702@mic.ucla.edu> <nq9sp2o@zuni.esd.sgi.com> <1992Jul28.215226.9960@ni.umd.edu>
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Organization: UCLA, Anderson Graduate School Of Management
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