SGI's are usually easy to add tape drives to, whether they're external tape drives or internal ones.  Most of the time, these are SCSI tape drives.  This page will assume a 120m DDS2 4mm tape and a 4mm DAT SCSI tape drive designed to work with an SGI.  Instructions for adding the actual tape hardware are in your SGI's user manual.  However, there are a couple things you need to keep in mind with SCSI devices:

• While you can mix wide/narrow and SCSI version 1, 2, and 3 external devices provided you have the right cables/adapters, the SCSI controller will slow-down to the least common denominator among your devices.  So, if you have a SCSI I tape drive, the bus will be as fast as if all devices on the bus were SCSI I devices.
• There are important cable length restrictions on external SCSI devices.  The bus will not function properly if these aren't kept.
• Do not mix differential and single-ended SCSI devices.  Differential devices use a different technology to allow longer cable lengths.  I haven't seen any differential tape drives, but I can imagine someone putting a single-ended tape drive on a differential bus.
• It's important to make sure the SCSI id on the device you're adding is unique for the SCSI bus you're using.  If not, the bus may not function at all.
• Beware of Zip disks and Jazz disks.  While IRIX now supports them, strange things can happen to filesystems with them.  Sometimes, they can cause a SCSI bus to not function.
• Use only computer grade DAT tapes.  Video grade isn't adequate for computer storage.
• Keep your tapes away from strong magnetic fields and heat.

    After you've added the tape drive and re-booted the system, you're ready to begin testing it out.  If you have any specific instructions for your tape drive from the manufacturer do them now.   If you have a graphical system, a tape drive should appear on the desktop.  In any case, the device file for the tape has been created, and, if this is the only tape drive on your system, it should be linked to /dev/tape.  The tape drive's device file is /dev/rmt/tpsXdY, where X and Y are the SCSI bus id and SCI device ID, respectively.  If this is the only tape, there should also be a /dev/nrtape device file that, when invoked, doesn't automatically rewind the tape the way /dev/tape does.  If it is the only tape drive on the system, you can usually omit any specification of the device file when running a tape operation.  If not, you'll need a -f argument in the "mt", "tar", "bru" and other tape accessing programs.  Test out the tape drive now by putting a blank tape in.  Enter "mt stat"and it should say there's a tape in the drive and something about the tape drive.  If not, enter "hinv" to check to see that the tape drive is present.  It's possible that IRIX doesn't recognize it automatically and that some changes need to be made.

last updated 2/28/00 by Martin McCormick, martinm@sas.upenn.edu