What do you want from a NAS

JonJ678 · 9 May 2009 at 07:06

Hey. This kind of fits under networking, hard drive, case and sff forums. I chose this one pretty arbitrarily.

What I'm after is a working specification for what a network attached storage device should be able to do. I've come up with my own, but it's always good to get different views.

Main:
Small, aim for smaller than most ITX cases
Accommodate four 3.5" hard drives
Reliable, replaceable components (+raid?)
Gigabit ethernet
Wake on lan + ability to run headless

Secondary:
Wireless connectivity
Capable of running bittorrent by itself
Quiet
Resistant to damage in transit
Cheap (this needs quantifying in the near future)

So, what do you think? Idea is to start off with a spec that comes pretty close to perfection, then compromise as required.

Cheers for any input

JonJ678 · 9 May 2009 at 09:21

Good shout on reliable. A NAS that repeatedly dies isn't worth having. Intention is four drives in raid 5, I've been very impressed by how resilient that has proven to be so far. I already have the drives, looking to free up space in my main computer with this project.

What it communicates with is a problem. It will have to be windows occasionally, so I'll need to learn a bit more about samba. I had sshfs in mind when I wrote the OP. This needs more thought.

The NAS devices on sale that hold four drives cost astonishing amounts, so assembling it myself looks sensible. matx is larger than I'm hoping for, if I can do this with mini itx + atom I will.

Cheers

JonJ678 · 9 May 2009 at 11:31

That's a good example of why I don't want to buy one. 290 quid exc vat, with 512 ram. The specs look suspiciously similar to the 70 quid intel board I've been looking at, so that looks like charging about 150 quid for the case and assembly. Reasonable I suppose, but if I cant make a case for less than a ton I'll be shamed.

What did you end up going with? Mdadm is excellent, I've been using it for a couple of years and am very pleased. Whenever it's gone down, through my own stupidity/experimentation, it's done a brilliant job of pulling itself back together.

Thanks for the warning about the northbridge fan, I'll have to do something about that. Not being able to track temperature doesn't matter so much after initial testing, and I'm hoping to attach two hard drives to the ide port so keeping the pci slot free. Good times

JonJ678 · 9 May 2009 at 15:31

Thanks again wonko, appreciate the input. I hope I don't go through that many stages! Unsure what to do about the expansion slot, as dimensioning and machining the case for it looks likely to be difficult. Have an initial spec, and first sketches of a case.

Intel D945GCLF2 (dual core atom, gigabit ethernet, shocking graphics, pci expansion slot. 2 sata ports, ide header that I hope to use as two more.)
pico psu, I think anything 90W or over will do fine. A bit worried about hard drives drawing a lot of current on start up, otherwise it looks reasonable.
four 750gb samsung drives, software raid. ubuntu server based.

There isn't a case available that suits this, which is an adequate excuse to play with metalwork during exam term. This will probably be steel as that's easier to source than aluminium. This will make it heavy, which should help with vibrations and so forth.

I'm never that confident with images, but presumably these will work for at least a while. The resolution is rather higher than Id hoped, but they're 90kb a piece so could be worse.
First draft

Second

First one allows some form of vibration isolation for the hard drives. Is taller and larger than the second. Easier to work with once assembled.
Second is about the smallest I can see this being. Square thing at one end is a 120mm fan. Any thoughts on whether one 120 or two 92 is the better idea? Intention is intake fans, and air leaves through holes in the back. Might put a fan on the back, having difficulties sketching the rear panel. All dimensionally accurate wrt the dimensions I've found so far, even the very ugly hard drives. I would love to know the height on the mini itx board, or the dimensions for the rear panel but intel have not told me this.

Assembly idea is 6 sheets of 2mm metal, four 8mm bars in the corners. Mechanically fixed. If steel, might weld the bars to the base plate. I'm not welding aluminium. I'm also aware that I'm meant to be making copper blocks at present, that's been placed on hold while I try to work out how long i'll keep the motherboard for.

Component price looks to be around 160 all in. 90 for board, 60 for psu, 10 on misc. Reasonable. So a few questions I guess

The current intention is to directly screw four hard drives into a rigid, heavy chassis. The only attempt at vibration reduction being http://www.overclockers.co.uk/showproduct.php?prodid=CM-005-AF What're the odds that this is a terrible idea? Vibrations will be transferred to chassis, and I don't really want this to make noise. I can't suspend the drives with the second draft, and sourcing grommets for hard drives appears impossible. Might make some. Is this worth the effort, or will directly screwing the drives into the chassis be alright?

One 120mm fan, or two 80/92mm? Fan speed not an issue, linux does a pretty solid job of that, as do inline resistors. Not going passive after a thread in the hard drives section, will blow air over at least one surface of each drive. I'm wondering how much effort I'm prepared to put into keeping this quiet, getting down to suspended hard drives and a single 7v 120mm would be nice but difficult.
Similarly, fans at front or back of case? Back is traditional, probably quieter, but might remove the option to use 120mm fans.

In-Win BM648 Mini-ITX Case is 6.8 litres, the second draft 6.3. Not exactly a massive space saving then. Cheers

JonJ678 · 9 May 2009 at 18:29

I have pretty much ignored cable routing so far. Hard drives arranged so that cables come out towards the front, so 8 cables to deal with there. The psu has few cables, nothing else has a wire running to it. Space either side of the fan on the front may be adequate. The board is 172mm long, the hdd 146 long, the bar 8mm square (probably). Leaves 10mm clearance. Pushing it a bit even for 90 degree connectors, good catch.

I think that means there's enough space for the heatsinks, cheers. Hard drive is 101mm wide, so easily 90mm between board and hard drives. No need to measure anything, but thanks for the offer

ATX spec covers the size of the I/O rear panel, but each board has different connectors. Better if things break to use the standard approach, so might do that instead of cutting out holes in front of each connector. Thinking outloud here, so sentence structure leaves a bit to be desired.
Uni workshop more than capable of this, I'll probably use a mill for absolutely everything. I don't really have time to machine it at present, but should do in a couple of weeks. Running cad between attempts to understand laplace transforms.

Nah, OS on the same array makes installation a nightmare and partitioning ugly. I've read that it works, but seems too much hassle to be worth it. Ill wire a 4gb usb stick up to one of the internal headers and install onto that. USB with ramdisks works pretty well, feels a bit sluggish as a desktop but definitely usable. As a box to ssh into occasionally and copy data to/from this should be fine.
If a disk fails, the array slows down a bit but otherwise works exactly as before. I used it degraded for a couple of weeks to see how well it performed, plugged the 4th drive back in and it rebuilt itself. No need to remember partitions, mdadm is excellent. All you need after a reinstall is a blkid | grep mdadm to find the uuid, then mdadm --assemble /dev/md0 uuid= most of the time.

Solution for damping. I have a load of 10mm diameter by 2mm thick silicon washers, 2mm hole. Drill a 5mm hole through the 2mm plate, countersink 10mm diameter to 0.75mm deep on either side. 0.5mm steel probably still strong enough to hang a hard drive off. Then screw in as hard drive : washer : countersunk side of plate : washer : steel washer. The silicon washers locate into the 10mm countersink so cant move laterally. The 10mm steel washer stops the screw tearing through the silicon. Fairly mechanically isolated. Not as good as elastic, but uses a lot less space. Perhaps thermal pads between hard drive and case. It would be useful to find 7mm hard drive screws, but they all seem to be 4 or 6mm. 1mm of thread in the hard drive isn't much, though I cant tear the screw out with pliers when it's that deep. I reckon the numbers work out well, ill draw it at some point to check.