Thanks!
I don't think there will be any difference between the SATA II or III HDDs. I look to what will work best in terms of data throughput, reliability and warranty. If the goal can be reached with SATA II drives for less money, I'll take that option. Likewise, if it's cheaper to use SATA III and get same or better performance, I'd do that.
Using identical drives is a good practice, of course, so if you're starting with less than eight, consider how you'll source buying more of the same drives later. I started with three RE-4s, using them internally in my Mac Pro while saving for the other five.
Oh yes - after happening upon some info about that, I would definitely use identical drives. I definitely also want to get all 8 up front for the TR8X+.
So I spent some time comparing various HDD brand/capacity/SATA version/price/tested on TR8X+ or not/RAID config options and found some interesting options.
All prices I noted were the lowest available based on online retailers that I know/trust, not necessarily the lowest price overall in every case. I'd rather pay a little more going to a trusted retailer than an unknown one and potentially deal with issues. Also all prices reflect new (OEM in most or all cases I think), not refurb or used.
Brands compared: WD, HGST & Seagate
Capacities compared: 2TB & 1TB
Among all the models I looked at, there's not much of a price point difference between SATA II and III. In the 2TB arena the lowest price was a SATA II drive, the HGST Ultrastar A7K2000 @ $200 from buy.com. The other five models I checked (including the WD RE4) ranged anywhere from $216 - $300. Of those other five models, four were SATA III and of course the RE4 is SATA II.
In the 1TB arena, the price point was very close overall between the three models I looked at, with a range of $120 - $131. The RE4 was one of the $120 models, as was the HGST Ultrastar A7K2000, and the Seagate Constellation ES was $131.
All that being said, here's what I'm weighing: Overall performance vs. reliability, present use vs. future use (as it pertains to storage space), and all of these as they pertain to upfront expense vs. long-term expense.
After doing some calculations from formulas on Wikipedia pertaining to potential failure rate in different RAID configs, I saw the advantage of RAID 6 vs. RAID 0 (even though the throughput is less, upwards of 700 mb/s for RAID 6 is very, very good considering the added level of file protection). RAID 6 would probably necessitate using 2TB drives so that I have plenty of disk space in the present as well as the future (12TB total). But the initial cost is higher.
On the other hand, there's RAID 0 with much higher throughput and less upfront expense (e.g. 8 1TB drives), but file protection may be more of a factor because there's no parity (though diligent, daily backing up is a safeguard against data loss). Then again, there's still a question of total space for future use (e.g. 16TB total using 8 2TB drives, vs. 8TB with the 1TB drives), in which case the expense is the same as RAID 6.
At which point, playing field being leveled, if I go with a higher up-front expense then I would either have 12TB and parity, or 16TB and no parity. With both options, I would likely put two or three 4TB Ultrastar 7K4000's in the internal bays for file backup, and of course an SSD for the boot disk.
I'm almost inclined to go the RAID 0 8TB route and think about expansion later, but not sure how I would go about that.
Okay, so enough of me thinking out loud. What do you think?
BTW, of the HDDs that Sans Digital tested for the TR8X+, the following are still available among the ones that are either 2TB or 1TB: HGST Ultrastar 7K3000, Ultrastar A7K2000, and the Western Digital RE4.
