Reader Madwand had this to say about RAID 5 NAS construction:
The SNB DIY RAID 5 and all the consumer NAS boxes perform much slower than what can be achieved these days, as illustrated by the sample performance chart below.
RAID 5 NAS Performance Comparison
The chart shows the performance of a simple DIY build I made using three-drive on-board RAID 5, on-board nVIDIA NIC (without jumbo frames) under Windows XP Home (OS on separate drive), which I measured using the same methodology as used by SNB.
This build was based on a now-dated Asus A8N-VM CSM with an X2 3800 configured to use a single core and 512 MB RAM.
The chart includes a couple of the higher-performing devices as benchmarked by SNB to make the following point.
Once you get into a NAS design, you quickly find that you have a ton of choices, and there is no single best choice for any of them. That is, it's really up to you how you design your NAS.
People get hung up on "server" terminology, box cosmetics, power consumption or other factors. But the reality is that anything goes -- from single-drive off-the-shelf boxes to the simple XP Home / on-board RAID and NIC that I used for the above example to ZFS and much more complex configurations. By the way, automatic sleep modes can also do wonders for power consumption these days.
Anything goes as well for pricing. Whether it's $500, $1000 or higher depends on what you want to spend. It's better to build the device to fit your needs and desires than to a price point, since the NAS will be a long-term central device of some importance to the household.