🚀 go-pugleaf

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