On Thu, 23 Jul 1998, VaX#n8 wrote:

> Tape Drive Questions:
> 
>     Drive: Archive/Python/Seagate 4586NP 4mm tape changer
> 
>     I have been noticing some strange behavior.
> 
>     First, the documentation I was given (in the form of some
>     photocopied sheets) is rather lacking.  In fact, the SCSI ID
>     jumper settings were left-right reversed.  This cost me quite
>     a bit of time to figure out.

See seagate's web page. There's a pretty good PDF describing this
class of drive.

> 
>     After the drive writes to a tape, it won't respond
>     to the Open/Close button (or the Step button, for that matter)
>     until the tape has been ejected, even if the tape is rewound.
>     Is this normal?
> 
>     On various occasions, I have witnessed the green "cassette" LED
>     to blink slowly, or the amber "drive" LED to blink quickly.
>     What do these mean?

Amber blinking can mean 'bad tape'
> 
> Hardware or OS questions:
> 
>     Controller: based on NCR 53c810
>     OS: a recent NetBSD (>= 1.3)
> 
>     Upon rewind, the drive retains exclusive access to the SCSI bus.
>     I can think of three explanations:
>         1) The drive does not support disconnect/reconnect.

wrong.

>         2) The controller does not support disconnect/reconnect.

wrong.

>         3) The OS does not support disconnect/reconnect.

wrong.

>     Any guesses?
> 
>     Furthermore, if the "offline" command is given, and the drive
>     does a long rewind, unload, reloads the next tape, and there

There's a jumper setting for this. See above.


>     are significant accesses to the SCSI bus during this time,
>     the machine does a hard reboot.
> 
>     Typical system logs are:
> 
> ... ncr0: timeout ccb=0xf0874000 (skip)
> ... st1(ncr0:6:0): non-media hardware failure, data = 00 00 00 00 44 bc 00 3c 00 00
> ... st1(ncr0:6:0): not ready, data = 00 00 00 00 00 00 00 00 00 00

Compile with SCSIVERBOSE. It's there so that the data lines above
are decoded into something more useful.

> 
>     The timeout is by far the most frequent.
> 
> OS question:
> 
>     I also had problems with the machine logging a line mentioning
>     a timeout, and the CCB being dequeued.  This frequently led to
>     a hung SCSI bus.  Thoughts?

Fix the above problems first. Mostly these drives are quite reliable.
Problems with them fall into these areas:

		+ Jammed or slipping rollers for the cassette.

		+ Generic DAT problem that once you write a media
		pattern onto a DAT, you have to degauss it to get
		a different media pattern, as well as other
		tape class interoperability problems (e.g., a
		DDS3 tape gives a DDS2 tape drive the fits).
		This often leads to tape drive timeouts, etc...

		+ Out of date f/w. Older f/w had problems. Check
		with seagate or your distributor.