Right now I cant get to the machine (off, in the basement) but it is some run-of-the-mill SATA drives using a SATA expansion card.

It works great but I just use it for /opt since I ran out time to move more of the machine into it.

You cant boot off the SSD, so I still use a SCSI but you can replace that too if you boot the SGI off the network.

Silent SGI:

Having gotten rid of the SCSI drives completely w/ the network boot, you can put a modern, more silent, PSU [1] (but hurry, ones w/ enough current on 5V (?) are rare), and then replace the GPU and CPU fans and turn of environmental monitoring.

[1] i had to replace mine; my 500 MHz Fuel is notorious for bad psu