BitScope Blade Rack 20 build (part 2)

Here is a picture of them without the flash so you can see the LEDs on the Pis. There is also a red LED at the end of each Blade Duo indicating they have power, although you can't see them in this photo as the red power plate covers them.

These 8 Pi3 model B+ have been running for a week or so now and haven't given any invalid results so far. I put that down to the better power supply than my USB chargers.

This is the power supply. These are normally used to run 12v LED lights in your ceiling (sometime called down lights) but this one is a 24 volt 10 amp output to make sure there is enough juice for all 20 Pis.

And this is the way they stand when one puts the rack parts around it. The top and bottom bits of the rack screw into the metal standoffs that you can see.

There is another pair of power plates and their 5 Duo's which stand next to this. However before I can do that I need to order more Pis.

BitScope Blade Rack 20 build (part 1)

You get 10 of these BitScope Blade Duo's. They hold 2 Pi's per Duo. You can see the power regulator circuit on the right.

You get a pile of 10mm nylon standoffs and M2.5 screws

Here is one of my Pi3 with its 14x14x14mm copper heatsink.

And it doesn't fit! There isn't room for the heatsink.

When I asked about this they said they don't normally use a heatsinks with them. They were kind enough to give me a number of aluminium heatsinks that are 5mm tall which would fit, however I haven't used them. Instead I bought more Pi3's rather than trying to remove the heatsink from the ones I already have.

Here is the first Duo in between the two power plates. One power plate is red and the other black so you don't mix up the polarity. The Duo is secured onto the metal brackets using M3 screws that are supplied. Due to the tight fit you add the Rpi after you've got the screws in.

And here is another shot of it before adding in the Pis.

Two Pis installed. The Pi plugs in via the GPIO pins and then you add the M2.5 screws to hold them in place.

Here I have done 8 of them, at which point I ran out of Pis. I need to add another Duo between the two power plates and this one is done.

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.