Thanks... for the tips... btw, which deskstar series would be good, there are several?? I was looking at the 7k3000 series
For high density HDD, I would go for lower RPM, here is why.
Coolspin (normally 5900 rpm). This about 18% less, but the data is pack so dense, that will make up the lower rotation speed.
We did test 5x 3TB Coolspin in our eBOX-R5, we got 250MB/s, where 5x 1TB 7200rpm only 230MB/s
and RM16_S6-R with 16x HDD we got over 1000MB/sec - I posted the screen capture somewhere in this forum.