This article has nothing to do with the speed of a Raspberry Pi as a server, unless the purpose of this server is to run "kopia".
I ran an 8 gig Raspberry Pi 4 with mirrored 8 TB spinning rust disks for quite a while. Performance is very good, once you stop playing with all the meta tasks and run, you know, server stuff. I ultimately switched to another system not because of CPU, but because of memory. SearXNG [1] likes a lot of memory.