I am looking to build an HTPC to stick behind the TV in the front room. I would install something like XBMC on it, so I can watch all my TV shows and films with that like your typical HTPC set up.

So this has few requirements, be small and quiet, very little actual storage need apart from obviously the media, and only just powerful enough to decode 1080p.

The NAS I want to build needs to support up to 6 3.5" HDDs. This already complicates a hybrid setup here because not many HTPC cases have room for so many HDDs. This would also probably go behind the TV in the same place as where I'd like an HTPC. But it may prove too loud, in which case it would be better off sited elsewhere.

This could be any size, should be as quiet as possible (but is it possible to get 6 3.5" drives quiet enough to be within 2/3 metres of you trying to watch a film with quiet parts?), and of course needs only consist of the bare minimum needed to link up to a network and manage a RAID5 array with mdadm.

SO:

At first glance it looks like it would be ideal to combine these two into one machine, but that limits me a lot on what case I need to choose. Unless I went for an off the shelf solution for both, but in that case there's not much room for me to play with customising things like software setups, which I do like to do. Especially as the NAS could essentially be an always-on Linux machine where I could run things like a home hosted website to share my media.

What I'm looking for is other users' experiences of having both a NAS and HTPC, what they think of them being best separately, are there any other usage situations you'd wished they were combined as one or it would have been cheaper/better value to build one machine? Are there any realistic case options for the two as separate units?

Please let me know if I should clarify anything. Thanks.

Generally, it's best to have separate devices. I've never combined them but I don't see why it would be a problem (other than the obvious: size, noise and need to bring down the NAS to upgrade or the HTPC or even for some software updates).
If you want a full computer for an HTPC (which isn't necesary nowadays) and can find a cheap enough HTPC-friendly case for your 6 drives, you'd save money by compining the components.
For the NAS, you definitely don't need a full computer even if you want to tweak software and use it as a public server. But with 6 drives, a full computer might be cost-effective anyway.
Noise-wise, whether you'd find the 6 drives quiet enough is a very personal issue and depends of course on your noise floor and the build.

A couple of warnings:
-there's no such thing as "just powerful enough to decode 1080p" (the encoding matters)
-RAID5 is trouble for the average home user and RAID is no substitute for backups anyway

Check out the Lian Li PC-q08 or Lian Li PC-q11. They both have room for 6 3,5" hard drives, and they are mini-ITX cases so they are smaller than the average case.

I've been running a HTPC for several years, gone through several hardware/software iterations, w/ the media files store locally as well as in a NAS.

First, XBMC is excellent. Good choice. It supports a network database seamlessly -- along with locally stored files if you want to split your media library for whatever reason. There is little or no user-perceivable difference between having the files on local drives vs a NAS -- assuming the NAS and network have decent performance.

If you go with a NAS, gigabit network is preferable. 100mbit works but can sometimes result it hitches/glitches, esp if you have multiple users on the network.

Even though there seems little need for a high performance CPU, it becomes very desirable as the media file database gets bigger. I have 20,000 songs, thousands of movie/tv/music video files -- browsing through that database with an Atom is doable but slow. Actually running a quadcore 3.3Ghz Athlon II 640 right now. Smooth, enough power for anything I do with XBMC, browsers, etc. Preferable to a dualcore 2.4Ghz Athlon I had in there before and way better than a recent Atom dualcore I tried briefly. The latter often had screen glitches whenever I stopped/ff/rw any HD video. Power consumption w/ 1TB notebook drive & 80+ Gold PSU is ~40W idle, 50s on HD play. It could be a bit lower with a Sandy/Ivy Bridge CPU, but it's low enough; as soon as the big plasma gets turned on, we're looking at ~200W anyway, so saving 5-10W here seems trivial.

The noise of 6 HDDs in a PC in the same room would be a bit much for me. But it might be OK for you. Have a look at the DIY SFF systems described in our massive Home Server build guide: http://www.silentpcreview.com/Silent_Ho ... uild_Guide

I am using a HP Microserver w/ 4 2TB WD Greens as a home server in a closet on another floor. Even with its fan swapped and slowed & the whole system sitting on a block of foam, it's not that quiet, but outside that closet, completely inaudible. It runs 24/7. It could easily be a DIY atom-based SFF PC.

I don't use RAID -- just a PITA, imo. I do use other PCs on the network to run backups of folders I consider important -- mostly the music files, as I rarely want to watch a movie more than once, even great ones, unless a decade has passed since the first viewing. This is good because even in mostly FLAC format, those 20,000 songs only take up <500GB, a trivial amount in these days of 4TB discs!

re: Mike's post
I don't think Atom boards are currently where it's at for a self-built NAS unless it's going to be a very small NAS. It's not a problem with the CPU as such but the boards. If you're positive you won't be needing more than 6 drives, check this for instance: http://www.overclock.net/t/1279524/asus ... -nas-board
It's mainly useful to pay attention to the energy efficiency of devices running 24/7.

Seconded.

I have a Q08 with six WD 20EARS (I think they're EARS) as an HTPC/NAS. It is audible (it's basically white noise, no tonality), but very quiet considering the number of drives - I don't find it noticeable over everyday life in the living room of a family home in the suburbs. If you live somewhere really quiet that may be a problem.

CPU-wise it's a first-generation Core i3, which is more than sufficient for the HTPC/NAS duties. It's running Boxee on Windows at the moment, it serves its contents to other Boxee clients around the house, and it's our shared iTunes library too.

(I might switch to XBMC when I can find a skin that my mother-in-law could cope with!)

The PC-Q08 is the case we used for our SFF home server build guide: http://www.silentpcreview.com/Silent_Ho ... e/Case_PSU The new http://www.silentpcreview.com/Lian_Li_PC-Q18 is mostly an improvement on the 08 for a home server.

There's no reliable audio/vibration data yet, but the new WD Red NAS drives look promising (SPCR thread) in big arrays. Six drives in one room is a lot though.

I've used both NAS+HTPC and NAS/HTPC configurations (max. 3 drives). In the end I separated them and moved the noisy space hog, the NAS, out of the quiet areas of the home and into a custom-made cupboard in the hall. The home is again silent, and any HTPC I may get only needs to be a slim media terminal box. Wouldn't have it any other way.

Regarding the server aspect, most prebuilt NASes seem to feature adequate software to provide that functionality - unless you want to run an actual website, in which case I think a hosting service would be nicer and cost-efficient. Even my old Buffalo single-drive NAS had a WWW-sharing functionality with proper access control and user accounts. Modern devices support everything from DLNA to FTP to torrents to clouds to browser-based sharing. They even run mail servers and more, and support plugins if all that is not enough yet.

My impression and experience of prebuilts is that they work efficiently and are extremely convenient. The price varies, but budgeting about 100 EUR per drive slot seems to get the job done over here with no drives in the mix. Sure, you can build the core yourself for less than that (just about) and get more raw performance, but the time saved, and the convenience and functionality provided would make me buy the prebuilt in a heartbeat.