> When ordering backups, do you mean of the actual backplane lane, or something else?
I mean the actual backplanes there are 6 in those units, sometimes a port (SATA port) will be bad, so its good to order > 1-2 spares.
As others have mentioned, RAID is not a backup, if you don't want to spend more money, use the other drives as backup drives and backup throughout the course of a week to different drives.
Are they all of the same brand? Or a mixture? How much do you want to protect your data? If you want a small HTPC, you could just get 2 x 4TB and put them in RAID-1 either with BIOS RAID (not great, but it works) or a RAID card.
Norco 24bay RPC4224 FTW (i use that connected to another box) with 10GbE, no expanders. NOTE though you may get a bad port on one of the backplanes, make sure to order a couple of spares so you don't have to wait for RMA.
>> I used four 1TB Western Digital RE3's (Enterprise) for a long time and was very happy with them. Not a single failure in 5 years.
I concur.
I am HDD-less in my main PCs for the most part now and put 4TB/RAID disks in another host.
If you are going for a NAS device, I recommend Synology, the 8-port model is $1000.
If you are building your own you can go SW RAID or HW RAID.
It all depends on how important your data is to you.
>> Is a good RAID card (4+ hard drive support) about $150+?
Most are $300+
I have a...
I went with 4TB Hitachi's, they go on-sale every so often to $189. Using them on a 3ware 9750-24i4e. Before that, I used 3TB Hitachi's, overall I like them (7200rpm variants).
I'm not sure you'll see a huge speed increase, especially with RAID-5 but a newer controller would be helpful. I...