I like the idea that we can use the documentation of another OS, and
those who are familiar with it, when discussing the handling of tapes.
This should make shell scripts more portable, programs like Legato and
Amanda work well with our tape drivers, etc.
-Brian

On Jul 9,  6:50pm, Matthew Jacob wrote:
} Subject: (2nd send) opinion sought about EOM handling for tapes
} 
} [ I sent this ought last week but didn't hear any opinions about 
}   this. Yet another bug at NASA/Ames related to EOM handling showed
}   up again- so I'd really like to fix it. I can do *some* fixing
}   without making the following change, but while I'm at it, I
}   thought it would be worth doing.
} 
}   Please respond one way or the other about this if you care ]
} 
} 
} Currently while writing if you hit EOM, that returns an EIO
} and complains loudly.
} 
} I'd like to change this to (and yes, this is swiped from a
} well known commercial OS, but the behaviour appeals to me. Well,
} it would....:-)):
} 
} 
}      When logical EOT is encountered during a write,  that  write
}      operation  completes  and  the  number of bytes successfully
}      transferred is returned (note that a 'short write' may  have
}      occurred  and  not  all  the requested bytes would have been
}      transferred.  The actual amount of data written will  depend
}      on  the  type  of  device  being used).  The next write will
}      return a zero byte count.  A third write  will  successfully
}      transfer  some  bytes  (as  indicated  by  the returned byte
}      count, which again could be a short write); the fourth  will
}      transfer  zero  bytes,  and so on, until the physical EOT is
}      reached and all writes will fail with EIO.
} 
} Until the EIO, no complaints to the console are necessary, or
} wanted (unless SCSIDEBUG is set). This allows trailing records
} to be written with some kind of warning the application that
} life is getting dangerous. The only risk factors here are for
} tape devices that cannot note hard physical EOT. This should
} only in fact be 1/2" reel tape, and, err, umm, just *how many*
} of these beasts are out there on SCSI busses at this point
} (a flood of email comes in....)...
} 
} 
} 
>-- End of excerpt from Matthew Jacob