One elephant in the room, is how I’m going to store the system whilst in operation.
The obvious solution is some sort of metal cabinet with provision for 19″ rack mounting and DIN rail equipment. Question is, how big?
A big consideration here is thermal matters. When going flat out, there will be 100W-150W worth of thermal energy being dissipated in there. So room for convection currents is a must!
Some decent fans on the top to suck the hot air out would also be a good idea. Blowing up so that dust doesn’t get sucked down into the works.
I figured I’d sit everything sort-of in situ. I figured out that the DIN rail mounts don’t have to go on the bottom, with these cases, if you remove the front panel there’s four holes for mounting those same DIN rail mounts on the front. So that’s what I’ve done. I’ve now got a DIN rail spare for future expansion.
If I try to pack everything up as densely as possible (not wise), this is what it looks like:
There’s room there for possibly one more node to squeeze in there. I’d think that’d be pushing it however. 5 is probably a good number, meaning we can space the units out a bit to allow them to draw air in via the gaps.
On top of the units I have my two switches. The old Netcomm 24-port switch was retired from our network when a lightning strike to a neighbour’s tree an 8-port switch, my Yaesu FT-897D radio transceiver, some ports on a wireless 3G router/switch, and an ADSL router out. It also did damage some ports on the big Netcomm switch, so in short, I know it has issues.
Replacing its 3.3V PSU with one that steps down from 12V would cost me the price of a 16-port 10/100Mbps switch brand new.
When we replaced the switch (paid for by insurance) we decided to buy a 8-port and 16-port switch. The 16-port switch, retired due to an upgrade to gigabit, is sitting on top, and takes 12V 1A input. It’ll be perfect for the IPMI VLAN, where speed is not important. It also accepts the DC plugs I bought by mistake.
The 8-port one takes 7.5V 1A, so a little less convenient for this task, I’d need to make a DC-DC converter for it. Maybe later if this works.
So considering a cabinet for this, we have:
- 5 nodes measuring 190mm in height: ~5 RU
- A 24-port switch: 1 RU
- A 16-port switch: 1 RU
- Some power distribution electronics: 3RU
Yes, the battery and its charger is external to the cabinet.
Judging from this, the cabinet probably needs to be a 10RU or 12RU cabinet to give us space for mounting everything cleanly and to ensure good ventilation. Using 8-port IPMI switches and 24+2-port comms switches, that leaves us with sufficient port space for the 5 nodes and gives us one port left for a small in-chassis monitoring device and 4 ports left on the main switch for an uplink trunk.
You could conceptually then consider these as homogeneous building blocks for larger networks, using Ceph’s CRUSH maps to ensure copies get distributed amongst these “cabinets”.