Powering Pi

I also did some work on the NFS server last week. Its a Pi3 model B+ with a PiDrive and the Y split power cable. It was plugged into one of my 5 port USB chargers which can provide up to 2 amps.

I plugged in a Seagate Expansion 3TB drive which has its own 12 volt power adapter. While copying the files across the power LED on the Pi kept going off for a couple of seconds before coming back on. Thinking the USB charger might not be up to the job I plugged it into one of the official 2 amp power adapters. Same problem. Even after I had unplugged the PiDrive so only the Seagate was plugged in the power LED still kept going on and off when accessing the disk.

The 2 amp official Pi power supply obviously is not enough. Its no surprise they have a 2.5 amp power supply these days. I decided to get a couple of the 2.5 amp power adapters to go with the two PiDrives and have gone back to using just the PiDrive.

I will have to try it again some time when I need more disk space. What I'd really like to try is having 3 or 4 drives plugged into a Pi with them running ZFS on Linux. Dream on. ZFS requires a 64 bit operating system and Raspbian is 32 bit at the moment. And then there is the lack of memory...

One node causes grief

I had problems with one of the Pi3B+ nodes in the cluster when I managed to lock it up. I thought I would power it down, put the SD card into another Pi3 and off we go. Of course that didn’t work. It decided it was going to lock the Pi user account so I was forced to wipe the SD card and reinstall which meant the 4 work units it had in progress were trashed.

The next problem was I couldn’t connect to the NFS server. It seems Raspbian has a limit of 16 connections at a time. I worked around that by logging one of the other nodes off so that I could copy the files needed.

After getting past that it decided to download the old Einstein app which doesn’t work under Raspbian Stretch so it trashed another 6 work units in quick succession. I had to update my preferences on the Einstein project in order to get it to download the correct app.

While adding/removing the SD card from this node in the Pi^4 case I also managed to break the fan power cable so the fans went off. I use USB to fan header cables which I got off eBay. The fans are plugged into this which is then plugged into the USB charger. The soldered join on the fan header pin had broken off. I had to resolder both. Just as well I still have a soldering iron. They look something this, except mine don't look as professional.

Blade Rack 20

In better news BitScope Designs have now got a Blade Rack 20 and a Blade Rack 40. I have ordered a Blade Rack 20 so I can get some of the compute nodes into a single case.

I also had to order a LED transformer, like they use for the LED down lights in your ceiling, to power it. The transformer has a 24 volt 200 watt output as recommended by the team at BitScope. The BitScope blades take 9 to 48 volts as input and provide 5 volts to the Raspberry Pi. Hopefully parts will arrive next week.

1st of September

Last week I added one of the Pi 3B’s back into the cluster. I thought I would see how it goes running the Seti Multibeam app. It was processing then around the same amount of time as the Einstein BRP4 work units (about 11 hours). Its now back to running Einstein work.

I have just added another Pi3B back into the cluster. That brings the cluster up to 12 x Pi3B+ nodes and 6 x Pi3B nodes. Unfortunately the ARM processors on the Rpi aren’t that fast. The Pi3B+ are about one hour quicker than the Pi3B. By comparison the i7-6700 can do them in one hour, which makes the Pi3 about 1/12th of speed of an Intel machine.

19th of August

I’ve been away for a few weeks so the cluster was powered off. The day we got back the electricity company were doing work in the street and there was no power for an hour or two. The cluster is now back at work doing Einstein BRP4 work after a few operating system updates were applied to all of the Pis.


Update: 26th of August
Einstein have this graph of daily credits. You can see when the cluster went off-line and came back on-line.