• Hi @bark, Welcome and nice to meet you. I skimmed Parts 1, 2, and 3, and I impressed. Let me give some quick comments. (1) The project is very well presented for newbies. (2) Of course it is an advanced topic in parallel/ concurrent computing, but using Open MPI and python make it not scary at all for newbies. (3) Of course newbies need to understand that it is not at all a weekend project. If you only know blinking a LED using python, you might need one year’s hobbyist time to complete the project. – tlfong01 14 mins ago   
• (4) For sharing storage, newbies might like to first try Samba and PureFTD sharing files with Win10. All Rpi might be a bit hard for newbies to develop and troubleshoot (Yes, I am a WinPC guy and sort of linux newbie.) (5) For mass storage, I am using 1/2Gb USB SSD and found it newbie friendly than HDD, because tthey just look like USB drives. (6) The project started 2018. Rpi4B appeared 2019 and a couple of things got greatly improved, including USB3, 1Gb Ethernet, both of which help making the cluster a couple of time more powerful and faster. (7) Python MPI is of course good, … – tlfong01 9 mins ago   
• Pyhon 3.7x already it self has mutl-processing (more newbie friendly than old style multi-threading). Of course python is ideal for google style concurrent processing, including TensorFlow which almost always uses python as examples. (8) We need to know this is kind of educational/learning project. We need to appreciate that we are not make use of GPU, and USB3, though so much faster, is still a severe communication bottleneck, limiting performance of parallel processing. (9) I have been reading similar Rpi based cluster projects these years, for learning, I would give 5 marks out of 5. – tlfong01 7 mins ago   
• Just thinking aloud, sorry for the typos. I have 4 Rpi4B 1/2 Gb, and have been playing with python 3.7 multiprocessing, 1/2TB USB SSD, Win10/Rpi3B+ Samba/PureFTD, etc. I also have a 4 years old PC with CORE i5, 6GB RAM, Nvidia, etc. As I said, Rpi USB3 slow communication and no GPU is the fatal weakness, Rpi x 4 can’t compare with single evil Wintel PC! 🙂 – tlfong01 just now   Edit

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