Usually, you think of solid state storage as faster than a rotating hard drive. However, in the case of the Raspberry Pi, the solid state “disk drive” is a memory card that uses a serial interface. So while a 7200 RPM SATA drive might get speeds in excess of 100MB/s, the Pi’s performance is significantly less.
[Rusher] uses the Gluster distributed file system and Docker on his Raspberry Pi. He measured write performance to be a sluggish 1MB/s (and the root file system was clocking in at just over 40MB/s).
There are an endless number of settings you could tweak, but [Rusher] heuristically picked a few he thought would have an impact. After some experimentation, he managed 5MB/s on Gluster and increased the normal file system to 46 MB/s.
There are several other settings we might have investigated related more to the actual buffering and reading of the memory card and I/O scheduling. However, [Rusher] shows you his methodology so if you want to use that as a starting point for further exploration, or you want to work with a different file system, it is still worth a look.
We tend to think of the Pi as an embedded board. But in reality, it is just another Linux platform and there’s been a lot of work done on optimizing Linux performance for different situations. We’ve looked at Docker-based clusters before, too.