By now we've learned to accept that Raspberry Pi enthusiasts will figure out how to use the single-board computers in new ways no matter how practical their experiments are. Serve The Home (STH) offered the latest glimpse into the realm of technically possible, but inadvisable, Raspberry Pi-nnovation by comparing the costs of building a server rack from more than 100 of the single-board computers with the cost of buying a Marvell ThunderX2 server.
We'll spoil STH's findings upfront: building a Marvell ThunderX2 competitor from a bunch of Raspberry Pi 4 units costs anywhere between 1.85x and 2.14x more than just buying an off-the-rack server. (The first estimate features 190 Raspberry Pi 4 units; the second features 220.) Setting up the Raspberry Pi server would be far more frustrating, too, because it involves setting up hundreds of units rather than just plugging in the Marvell server.
So why even bother estimating the costs of building, operating and maintaining a server made from Raspberry Pi 4 units? STH explained that it met with "a Silicon Valley dev-ops team" using "shelves of ODROID and Raspberry Pi devices instead of traditional servers" for their Android continuous integration / delivery pipelines. The team would rather use these single-board computers than emulate Arm processors on x86-based servers.
STH then figured out how one could assemble such a Raspberry Pi-based server and compared it to a Gigabyte ThunderX2 server. It found that building the former cost roughly $111 per Raspberry Pi 4 4GB node, which totals $21,254 for the server featuring 190 units and $24,609 for the one featuring 220. The Gigabyte ThunderX2 cost just $11,500 in comparison. (All of these figures would vary, of course, based on configurations and discounts.)
Finding new uses for the Raspberry Pi 4 is always interesting; we've even overclocked the Pi 4. But unless someone is vehemently opposed to emulating Arm on an x86 server, or content to answer "because I could" whenever someone asks why they bothered to set up hundreds of single-board computers instead of just buying a server, this definitely seems more like an experiment than the future of computing.