Brand doesn't matter and size doesn't really matter either in most cases. You can put a 250 Gb with a 320 Gb and it will work. The downside is that all of the drives will match the size of the smallest one. So the 320 Gb one "loses" 70 Gb of space because the smallest one is 250 Gb. If you run JBOD though, size doesn't matter because the drives are combined and the storage capacities are added together (250 Gb + 320 Gb=570 Gb). If you run the It is best though and most cost efficient to stick with drives of the same size so that doesn't occur though.