Recovering data from 4mm and 8mm tapes

[Douglas Taylor]

I've been recovering old data from computers that I used many years ago, 
the last effort was trying to recover the data from a hard disk that ran 
a WFW 3.11 system.  The problem was the disk could not be read on a 
modern computer, so I recreated an old system and (very lucky for me) 
ftp'd the data off the system after I found an ISA network card.

I have a couple of 4mm and 8mm tapes that contain data I want to 
recover.  The 4mm is DDS-1 and was written using tar on a SGI system in 
1998.  My questions are;

  'What modern DAT tape drive will read this tape?  How backward 
compatible is this technology?'

This seems like an easy problem and intend to use a linux system to read 
the tape.

The 8mm tapes were also written on an SGI system, however it was in 1994 
and the IRIX Backup utility was used.  IRIX 5 was probably used.  Any ideas?