OH! I had one more question I didn't see on the product web page. Does it have a processor and RAM? Can the RAM be upgraded?
Yes, the DNS-345 has a CPU and RAM. The DNS-345 is essentially a computer in and of itself, running a Linux kernel. The DNS-345 has a 1.6 GHz CPU. I don't know the RAM size off the top of my head, although that shouldn't be a prevailing factor impacting performance. I don't believe the RAM is upgradable, but again, I don't think the RAM will be a bottleneck for performance.
Also, how easy is it to get drives in and out when one goes bad? How does it warn you a drive is/has failed? I assume this not a hot swappable device.
Removing a HDD involves powering down the DNS-345, pulling off the front-face of the unit, and sliding out the HDD. The process should not take more than 30 seconds. The DNS-345 is not hot-swappable, i.e. the unit must be powered down to remove HDDs.
The DNS-345 web UI displays the health of each hard drive in the unit.