This weekend’s task is to convert an ageing and awkward file server into something more manageable. I’ll do this by basically replacing the current controller (an old laptop) with a Raspberry Pi, and shoving everything into a box.
Firstly, an apology: I’m a hacker, in that when I create something, it will work, but it may not be pretty. I’ll leave the works of art to others, and focus on what I’m good at: solving the current problem with what I currently have at hand.
Here is the old system:
Four hard-drives, a laptop, a USB hub, lots of cables, lots of power supplies.
The goal is to cut it all down into just one box, one power cable, one ethernet cable.
So, first, I got an old ATX power supply from a machine I had lying around, and converted it so it didn’t require a motherboard to run.
To do this, open up the power supply box, remove any cables (leading to outside the box) that are not red, orange, black or yellow, and connect the green cable to one of the blacks (remove some of the insulation from the black cable first, obviously). The green cable tells the power supply that it’s okay to turn on.
While in there, I cleaned out some of the dust and fluff, and neatened the cables a little. There are four voltages that come from the power supply unit: 0v (black), 3.3v (orange), 5v (red), 12v (yellow). I wasn’t sure how many of each of these cables are actually needed to supply enough current, so when I was pruning cables from the ATX box, I just left these all intact.
Next, I laid out everything in a way that I thought made sense:
If the cables are removed, then the above will fit into a box that’s 27cm x 27cm x 18cm, with a few millimetres spare on sides and top, and a few centimetres at the back. We need the space at the back so we can re-organise the cables.
So, I cut out the pieces for the box walls. The wood I had (which I scavenged from the attic “floor”) is 1.2cm in width, so the panels I cut are:
- two 27cm x 27cm, for bottom and top of the box
- two 27cm x 15.6cm, for front and back
- two 24.6cm x 15.6cm, for side walls
The last two, I left a little shy of 15.6. Partly because of ventilation, but mostly because I forgot the old adage to measure twice before cutting.
I put the floors and walls of the box together, with wood glue and screws.
Next, I needed to make the power rails. After a little thought, I decided to use two coat hangers (yes, seriously!), straightened then cut into four lengths of 27cm each. The resistance of each length was between .5 and .7 ohm, so I was pretty sure they’d do fine.
I drilled holes at the back end of the side walls and put the rails in. I’ve been told since building the thing that this setup may cause electro-magnetic interference – especially as the rails look a bit like aerials. If it causes a problem, I think I’ll need to coat the box with metal.
Next, I started wiring up the PSU. First, I placed the PSU in the box and measured roughly how long the cables should be, then I cut them about 3cm longer than that, and stripped the extra 3cm of each wire.
I then tied each wire to a rail making sure the stripped area of the wire was in full contact with the rail. Orange (3v) at the bottom as it’s unlikely to be used, then red (5v), black (earth) and yellow (12v) at the top. In retrospect, the 12v and 5v should be the other way around for neatness, but I didn’t think of that at the time.
Most hard drive enclosures use a 12v input, so what I did next was to take the hard drive power supplies, snip the cables so they were about 15cm long from the hard-drive end, then strip the ends and wire them up. The cables were wrapped in black plastic, the “live” wire having a broken white line printed along it. I connected the live wire to the 12v rail and the other to the 0v.
Next, I took the case off the USB hub, and screwed it and the Raspberry Pi to the underside of the case’s box.
The power supply for the USB hub is 5v, and when I stripped it, I found this was indicated by the live wire (5v) being red. I left this cable longish (about 30cm), so I can hinge the top of the case and open it without disconnecting anything.
Power for the Raspberry Pi is supplied through a micro-USB cable. I scrounged one from somewhere in the house and stripped it down to about 30cm in length. The cable has four wires – black, red, green, white. We only need the red (5v) and black (0v).
Finally, I inserted all the hard-drives with USB cables connected, and hooked it all up. I’ll need to get shorter USB cables to neaten it further, but the original cables will do for now.
Software-wise, I used Raspbian for the operating system, and ZFS for connecting the drives together and serving to the network as one large hard-drive.