I have a Super Flower case that used to house a PC I've since parted out. It looks just like this one (but is a dignified silver rather than red).

 

 

Can I just put a pair of these http://www.newegg.com/Product/Product.aspx?Item=N82E16817121912 in those four 5 1/4 inch bays? Any "gotchas" with a gizmo like this with unRAID, maybe with regards to the drives spinning down or something?

There are several gotchas, including added heat (less space = less optimal cooling), more noise (to combat the first gotcha, it adds a fan), and yet another source of mechanical problem (connections, rattle, etc.)

 

However, a lot of folks are using them, as will I once my drive space requirements grow. 

 

However#2, I haven't seen that brand before.  You may want to scan the boards for the brands folks use and see who likes what.

 

 

Bill

that LOOKS like the AMS backplane that Tom's using, but those are different trays.

Well....as in many things in life...the answer is "it depends". 

 

As Billped points out, these type of stacker units allow you fit more drives into a smaller space.  And with more drives comes more heat and more noise.  In addition, more drives put more load on your power supply, particularly when they first spin up.

 

But here's where the "it depends" part of my answer kicks in.  IF you have a large enough power supply (look elsewhere for best attributes) and your current level of heat/noise isn't a big factor (either because your case has plenty of airflow, you live in near the North Pole, etc.), then adding the stacker units shouldn't be a problem.

 

I, for instance, use two 4-in-3 units in my rackmount case and like them a lot (6 of the 8 slots are filled with SATA drives and two IDE drives are mounted internally).

Thought I'd follow up and say that I installed a pair of these 3 in 2 iStarUSA SATA bays. I had four 5 1/4 inch external bays, so the 3 in 2's made sense for me. Plus these had grooves that enabled them to be fitted in the bays without bending anything in the case. BTW, these iStar bays look just like the bays from other manufacturers. I'll be some other company makes them and they're simply rebranded.

 

Anyway, they seem to work great. The drive temps are actually about 2 degrees cooler than when the drives were installed conventionally...generally between 36 and 39 degrees when they're spun up. Five of the six are filled. Probably not really necessary right now, but they'll be handy when I inevitably have to move into a larger case.