The internal SCSI bus in an Indigo2 is of course an 8 bit bus, and therefore has termination for those 8 data lines and the 3 address lines that go along with it. At least some of the drives you linked to are 80 pin SCA, that implies a 16 bit wide data bus, with 4 adress lines. Those extra 8 data lines and the 1 address line are not terminated by the resistors already installed in the Indigo, they just plain aren't connected. Back when I had an Indigo2, the brand new IBM drive I bought refused to work, because it wanted all those floating lines terminated as well. The SCA adapters I have here have an optional little extra board in one corner that's called "9 lines terminator" with a bunch of resistors, a transistor and a few capacitors.