SCSI CDROM changers and cdrom.nlm?

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2 total messages Started by U58252 Tue, 12 Dec 1995 00:00

#519

Author: U58252
Date: Tue, 12 Dec 1995 00:00

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I have a friend that wants to put up an application that requires multiple
CD-ROM drives on a netware 3.12 network. Performance is not a major issue,
but just want to not have to physically insert media continuously; and still
do it cheap. We notice there are a few changers out there (NEC,Pioneer,?)
that may fill this mini-jukebox requirement.
A few questions come to mind,
Do they implement it so that each disc is a seperate SCSI ID and LU?
If so, are the ID&LU range selectable?
Or does it just look like one drive with some extra scsi disc-selection
command. i.e. do we need special software to do the switching and
Netware volume mounting and drive mapping? Will cdrom.nlm work with
these (or any?) of these drives? Recommendations and comments welcome.
SCSI controller is a FutureDomain1680. ok?
Thanks.

Re: SCSI CDROM changers and cdrom.nlm?

#518

Author: Rhia
Date: Wed, 13 Dec 1995 00:00

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In article <95346.205816U58252@uicvm.uic.edu> <U58252@uicvm.uic.edu> writes:

> I have a friend that wants to put up an application that requires
> multiple CD-ROM drives on a netware 3.12 network. Performance is not a
> major issue, but just want to not have to physically insert media
> continuously; and still do it cheap. We notice there are a few changers
> out there (NEC,Pioneer,?)  that may fill this mini-jukebox requirement.
>
> A few questions come to mind, Do they implement it so that each disc is a
> seperate SCSI ID and LU?  If so, are the ID&LU range selectable?

There are both kinds.  You can easily put together a tower containing
individual CD-ROM drives, each with its own ID.  Procom Technology makes
towers of this sort as well.

> Or does it just look like one drive with some extra scsi disc-selection
> command. i.e. do we need special software to do the switching and Netware
> volume mounting and drive mapping? Will cdrom.nlm work with these (or
> any?) of these drives? Recommendations and comments welcome.

CD-changers or 'jukeboxes' are more likely to be this sort of device, which
appears as a single SCSI ID with multiple LUNs (Logical Unit Numbers)
within.  The ID is selectable, but the LUNs are not.  A changer is a single
read mechanism with storage space and a disc mover to select which platter
to put into the mechanism.

There are also CD towers which appear as a single SCSI ID with LUNs inside
but still have independent mechanisms for each disc.  In this case, a
special-purpose SCSI adapter acts as the intermediary between the initiator
(your host adapter) and the target devices.

I'm not sure it's a very good idea to put a changer on a server, because
only one platter can be available at a given time in the device, and if you
have multiple users trying to access different discs, somebody's going to
have to wait, and the unfulfilled wait can cause a bus timeout and all
sorts of problems with the drivers.  The CD tower, either as independent
IDs or as a multiple-LUN device, would be a better choice because of the
multiple mechanisms.  The issue is not the LUN support but the number of
CD-ROM spindles and read heads.

Rhia

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