Reading a DDS tape with 2M blocks

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I have a DDS tape (written on an IRIX machine) with 2M blocks.
Any way to read this on a NetBSD machine?
My memories of SCSI ILI handling on DDS are fuzzy. I remember you can operate 
these tapes in fixed or variable block size mode, where some values in the CDB 
either mean blocks or bytes. I thought in variable mode, you could read block 
sizes other than the (virtual) physical block size of the tape.