Summer has been busy and it’s now behind us. I won’t annoy you with all the details of what happened but I wanted to come back on a project I started a few months ago with my kids. I called this project CLEGO.
CLEGO stands for Cluster for Learning and Exploration of Global Observations, or simply, Cluster made out of LEGOs.
The idea was to build a silent, compact, and very powerful cluster to study Apache Spark in a dedicated, non-cloud, environment.
I initially thought I would 3D-printer the parts, but quickly realized I would be crazy (or crazier) if I wanted to design all the parts then printed them. It made sense to go with LEGO, specially as I was not on my coup d’essai, I built an entire data center in LEGO back in 2006. If you do not want to see the whole video, the data center part starts around 1:41 – and, yeah, be tolerant: this video is more than 10 years old and I did not become a famous YouTuber thanks to it.
Picking up the Right Hardware
It starts with the CPU. No way I could go with AMD, I also did not want Xeon for their price tag and consequence on the rest of the hardware (ECC memory, larger mainboard…), so I settled on used i5-6400T. They have 4 cores and 4 threads, run at 2.20GHz, but mostly their TDP (Thermal Design Power) is only 35W. The non-T version (i5-6400) dissipates 65W and only runs a little faster. Those are the CPU you would find in laptops.
Now that I had the CPU, I need the motherboard. I looked quite a bit to find a board that would have 2 network connectors or 10Gbits/s but I settled for the Asus B150M-A/M.2. The form factor (Micro ATX) was a good reason, I still wanted something compact. But 4 DD4 DIMM slots and USB 3 made the cut. If I could not get faster or more Ethernet on the board, I could still plug in a USB3 adapter.
Memory was a no brainer. I wanted DD4, max out each node to 64GB, so I picked the Corsair Vengeance kit: LPX 32GB (2x16GB) DDR4 DRAM at 2133MHz (PC4 17000). As much as it was a no brainer, it was the most expensive line of budget in this project. But hey! My cluster has 256GB of RAM, that’s the size of my SSD drive on work laptop.
As the level of noise was a real priority, I did not want mechanical drives for storage. I was at first thinking about classic 2.5″ drives, but settled for m2 “drives”. After a little bit of research, I decided on Intel’s SSD6 series, which are basically NVMe drives. Those drives have pretty awesome specs: sequential read up to 1775MB/s, sequential write (up to) 560MB/s, and 128.5KIOPS. I picked 512GB, if I need more, I can still access my 12TB SAN.
Despite have low wattage processor, I still felt like having a dynamic airflow on the CPU. This is done by a Cooler Master GeminII M4 CPU Cooler. They have 4 direct contact heat pipes to drain those calories out. However, the most interesting aspect for me was the variable speed fan and the very, very low sound level. I must admit I really like the great Cooler Master packaging and engineering for the metal parts and thermal paste. It’s definitely a great product.
I thought I could work with only two power supplies on the rather high wattage. I went with a couple of SeaSonic SS-520FL2. They are fan less and display a 520W output and modular cabling: in my scenario I need a PSU to feed 2 motherboards and 2 CPU. Therefore I did not want additional cables to use valuable room. The unit comes with enough cable for one motherboard and two CPU, so I had to get an Eyeboot ATX 24-Pin Female to 24-Pin Male Y splitter power cable.
Network is assured by a TOR (Top of Rack) switch, which consists of a basic, but efficient, Netgear GS108Ev3 8-Port gigabit managed switch. Originally, I wanted 4 ports for the 4 nodes, 1 port for output, and 1 port for a Raspberry Pi to monitor the environment (temperature, etc). But I left this last idea out for now, meaning that a 5 ports could have been enough.
Speaking of ancillary equipment, I also included a 4-port KVM from Iogear, GCS24U. It’s a little bulky (specially with all the cables) but I like the idea of a “remote” switch (a cable) so you do not have to have the switch next to the cables.
Despite the low heat of the CPU and the fans, I wanted to make sure that the hot air would not stay on the motherboards. The power supplies are also fan less, but we still need to dissipate those calories. I added the AC Infinity Airplate T7 to the system. It provides a really quiet cooling with a thermostat control, which allow for precision temperature control. This is usually used for home theater AV cabinets.
We are now ready for assembly.
Building the Chassis
Final Dimensions & Thoughts
CLEGO measures about 25.4cm (10″) x 50.8cm (20″) x 42.2cm (16.6″). It now rests on a monitor stand, so I can have it under my desk, instead of “on” my desk. It is “pretty” heavy. I will have to weigh it sometimes, but moving CLEGO is always a challenge.
It was definitely an interesting project, but now, the more difficult tasks are coming: install and optimize Apache Spark to leverage this power. Look forward to more articles on this, hopefully soon!