--On Tuesday, August 27, 2002 10:28:02 -0400 Jon LaBadie <jon AT jgcomp DOT 
com> wrote:

Has anyone else noted this behavior?
    "mt rewind" returns (completes) before tape is rewound

Yes, it seems to be fairly a common behavior of tape drives.
Back in the days when I had to write shell scripts to do
backups, I always threw in a sleep call after any tape command.
Not all commands needed it, but wasting a few seconds on a
several hour job was much better than the random error that
would cause the entire job to fail.


Frank

Specifically,

When I issue an "mt rewind" from a shell command line,
the tape begins to rewind (lights on drive blinking)
and after about 10 seconds the mt command completes
and I get my shell prompt for the next command.

However, the tape has not yet rewound completely,
the drive lights are still blinking.

If I issue a second mt command (another rewind or status)
that command blocks until the tape is completely rewound
before executing and returning.


I'm wondering if this is why my amcheck command sometimes
fails to find the correct tape in my changer though amdump
always does.  Perhaps amcheck does an mt rewind and  it
returns before the tape drive is done rewinding.  Then
amcheck might issue a command that times-out rather than
blocking and thus amcheck thinks that slot has no or the
wrong tape.

Just musing.

--
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
 4455 Province Line Road        (609) 252-0159
 Princeton, NJ  08540-4322      (609) 683-7220 (fax)

--
Frank Smith                                                fsmith AT hoovers 
DOT com
Systems Administrator                                     Voice: 512-374-4673
Hoover's Online                                             Fax: 512-374-4501