[willemd]

As a system builder (computers) for 20 years, I have to disagree with some of these recommendations.

Hard drives; I've got boxes full of failed cheaper commercial hard drives of every sort, including many WD Caviar Green drives, and SSDs from every manufacturer including Intel. Green drives are meant for PC storage only, and only on PCs which are shut down when not in use. Heat can be an issue, but not nearly as big an issue as the components of the hard drive itself. WD Green drives use the cheapest components of all WD drives. The only difference between a WD Green and any cheap WD 7200RPM drive is that the motor is set to run slower RPMs by sending less voltage to it. This supposedly allows them use slightly less power (almost immeasurable in reality). But I've never seen that they run measurably cooler than any WD 7200RPM drives. Also, if your case doesn't have anti-vibration mounts, a Green drive may run a bit quieter.

The Western Digital Green series drives may last for a while if your NAS/HTPC is often turned off - or they may last for 15 years of 24/7 usage. Or they may barely make it through the warranty before they die. The same can be said of any cheap hard drive. When running, and even when not in use by you, your storage drives will be spinning up and down as the OS monitors them (particularly so if you use any version of Windows - unless you adjust the cache and search settings, and who does that?!) - not to mention when they're being scanned by anti-virus and anti-malware. Bottom line is that no cheaper commercial hard drives are designed to be run 24/7, which most NAS devices and HTPCs will.

This is why manufacturers make hard drives specifically for NAS and servers. I'd recommend Western Digital Red series for NAS/HTPC, for both the OS and storage. Create a separate partition for your OS, and back it up whenever you make changes to it with an image backup system (by far the most economical, trustworthy, and complete backup solution). These WD Red drives cost a bit more for a reason, they're proven to last under much more strenuous testing methods. The motors, armatures, and plattens are better components. I've yet to see (knock on wood) a WD Red drive fail for me or my customers yet. That's not a guarantee that they will never fail, all drives fail eventually. But for the increase in price, the track record of dependability for WD Red drives is well worth it in my opinion. Green drives with lower RPMs (usually 5400 or about) from any manufacturer cannot compare for dependability in any situation.

For mechanical drive sizes, I agree that 2TB is the sweet spot for many reasons. Keep in mind that anything over 2TB drives will need to be formatted into more than 1 partition with most operating systems. Not so bad for the technically inclined, and a nightmare for some who aren't. Also, Windows can only see so many partitions at a time (8?) including optical drives, so not like you can load countless smaller drives. There are 4TB and 8TB drives available now. Cost effectiveness depends upon the size of your collection and how you connect them (how many SATA connectors for internal, USB connections for docks, and how many slots for NAS). I've never used nonRAID, but RAID is still limited to 2TB partitions on most operating systems such as Windows. I'd think nonRAID would be the same in that regard.

SSD; Flash memory (used by SSDs) has a limited number of reads and writes, and the technology is far from bug free. Just do a search for failed (insert the manufacturer and model of your choice) SSD and you'll quickly find that they have as high failure rates as mechanical hard drives. So that's up to you if you want the highest price per GB on the market and latest technology.

I also disagree that an SSD for the OS is going to provide any noticeable speed increases once loaded with the OS and software and given some time. At first they are a bit faster, just like any new drive, but that doesn't last. Personally I use 2x Corsair SSDs in RAID 0 for my HTPC/gaming/everyday computer OS. When doing read and write speed tests, it comes out considerably faster on the graphs than mechanical drives. But in real world use, I notice no difference from my last RAID system with mechanical drives. My games don't start or play noticeably faster. Files don't open noticeably faster. It's only slightly faster at boot than my 5 year old RAID array was with 4x 1TB Samsung F1s (was 12 seconds faster after installing the OS 2 years ago, and is now only 2 seconds faster). At this rate, after 5 years it will be actually slower at booting than the mechanical drives were.

RAID; I've been a fan for years. But I wouldn't recommend RAID for the average user because of the time and effort involved in setup and reconfiguring when something breaks in hardware and software (all Windows OSs are notorious for breaking arrays with perfectly good hardware). If you insist upon running RAID, I'd recommend having a good image backup system as well. You WILL need it eventually.

NAS vs Internal Storage vs Docks; I see absolutely no advantage to NAS over internal storage, other than it may possibly be easier to physically access in some situations. But there are quite a few disadvantages to NAS. NAS devices are typically noisier and hotter than PC cases and docks, and comparable to HTPC cases. You have the added headache of network configuration with a NAS. The tiny fans always get dirty and become noisy. If the fan fails, the hard drives are subjected to much more heat than any other option. It can be a serious headache if your NAS fails, or a wireless network connection fails while transferring files. Which files transferred and which didn't? They don't transfer alphabetically or any other logical sequence that I know of. Either manually check each one, or copy the entire lot again to be safe. And I've seen files become corrupted when being read from a NAS device when the wireless network connection failed. You don't have those problems with internal storage or docks. Docks provide by far the coolest environment for hard drives, but vibration can be a factor for noise depending upon the surface used. We've tried several NAS devices in the past, and always ended up eliminating them for internal storage or docks. Internal storage is always my preference, unless I need to change hard drives in a hurry - then I prefer a dock.

I've currently got 4x 2TB drives inside my full tower Antec 1200 case, plus the 2x SSDs (seen to Windows as 1 drive in RAID 0 array). I use several 2TB drives in a couple Welland docks connected with USB2.

Which brings me to Fully Uncompressed 1080p movie files; I've never had an issue with USB2 speed for playback. Never. If you have, I'd suggest that the constraint is something other than USB2 speeds. EG; high cpu or memory usage when other things are running in the background, or inadequate memory in your onboard or separate graphics card to cache ahead at USB2 speeds. With many older onboard graphics chips or low end graphics cards it was a problem. It's quite easy to find a low end graphics card today with a tiny fan (again, they can get very noisy) or fanless with 1GB of memory. And most onboard graphics today easily handles USB2 speeds.

The bigger problem with USB2 is file transfer speed, which is a valid concern for most HTPCs as you add files to your library. If you go with a dock, consider one which has E-SATA for much faster file transfers. Then you need to make sure your motherboard supplies an E-SATA connector, or purchase one separately. USB3 is much faster. The same goes for NAS, depending upon wireless type and even Ethernet connections (10/100 or Gigabit), you may have slow file transfer speeds. Nothing beats the file transfer speed of internal drives, USB3, and E-SATA - which are all limited only by hard drive write speeds (which is why I prefer RAID 0).

Fans; the bigger the fan the quieter it will be while moving the same amount of air, without exception. Smaller fans require higher RPMs to move the same amount of air as bigger fans at slower RPMs. Be careful about small low RPM fans, which may not move enough air to cool your system. You can spend more on "silent" fans of any size, but as they get dirty around the moving parts (and they always do) they become as noisy as any other fan of the same size and RPM.

Cases; HTPCs are often chosen for their aesthetics, rather than their function. The problem with most aesthetically pleasing HTPC cases (and NAS storage devices) is that they're often too small for anything but small and noisy fans. If aesthetics is your priority, the trade-offs are heat and noise. And if those fans fail, all components of the HTPC are subjected to extreme heat - and heat kills electrical components.

For best function, consider a mid-tower case with a top exhaust fan of 6" or more for your HTPC which will not only house as many hard drives as you'll need while keeping them cool, but also do so quietly. Or consider custom fitting a large exhaust fan to the top of a flat HTPC case - usually means cutting off the top and drilling some holes. With a tower case, because of the larger area inside and at the joints, even if your only fan fails it won't trap comparable heat to a smaller HTPC or NAS case. Unless your TV is mounted on a wall and you have no media center, you can usually hide your HTPC in back of the TV itself or media center (that's what I do). I never need to get at my PC anymore, other than to clean it every 3 months or so. No one other than me knows it's there.

I use a full tower Antec 1200 for my HTPC. There are countless better and smaller options available today. It also has a higher end graphics card and doubles as my gaming/everyday PC. It has anti-vibration housings for hard drives and sits on rubber feet. I only use the top exhaust fan on the case at the slowest setting. If not for the graphics card fan (and only when playing demanding games), it would be completely noise free - unless I stick my ear against it to hear the top fan. And ambient temperature inside the case never goes above 38 degrees C in South Australian summers.

Remember, a PC/HTPC/NAS case should always have negative pressure inside, meaning more fans blowing out than in. Unless you take steps to make it so, they're far from air tight and will draw air in easily from several places.

Whatever you use for a case, try to keep it away from the floor, pet hair, and smoke to remain as clean and thus as cool as possible.

We generally avoid cheap low end parts, and expensive high end parts. Both have consistently had higher failure rates than parts in between. At least that's been our experience from building countless computer systems over the last 20+ years. Hope this helps someone narrow down their options.

WD Red series are only advantageous for hardware based RAID servers because of their TLER function. They will give up reading faulty sectors far earlier than regular drivers, because hardware RAID controllers don't wait for drives that lock the array. For desktop or HTPC use this will increase the chance of read errors on the Red disks.

As far as you dismissing SSD's, that's just nonsense. In all normal uses for an HTPC (in which regular users definitely don't use a (loud) 4-fold RAID system), an SSD is so much quicker than mechanical hard drives. Especially with Kodi loading so many small files (thumbnails, backgrounds) or small read/writes (the database). Their reliability has also increased greatly in the last few years.

Your advices should be taken with quite a grain of salt for non-niche users.