I have a Pegasus R4 (8tb) raid and one of the disks has gone down. It is a Hitachi HDS72302 (2 tb) Do I need to replace it with a new Hitachi HDS72302 or can I use a different one? if I can does anyone know what ones are compatible with an R4 raid?
yes, you have to use a new HD with exact the same Modelnumber. In your case it is a Hitachi Deskstar 7k3000, 2TB, HDS723020BLA642.
How old is your system? If it is 5 years plus, you should replace all drives. After ca. 50.000 hours running time, HDs reach the end of their lifetime. In your case, because you run your Raid probably on level 5 it could happen that during the rebuilt process another HD fails. In that case you would loose all data. I believe you have a back-up.
There is a compatibility list on the promise website for all drives you can use with your raid. But you can't mix them. All drives must be the same.
Mac pro 8core
several raid systems