That is odd. It likely has something to do with the index caching and how many replication volumes you configured. By default it indexes all file metadata in RAM (I think) but that wouldn't justify that type of memory usage. I've always used mostly default configurations in Docker Swarm, similar to this:

https://github.com/cycneuramus/seaweedfs-docker-swarm/blob/m...

Are you claiming that SeaweedFS requires twice as much RAM as the sum of the sizes of the stored objects?

Correct. I experimented by varying the data volume, it was linearly correlated by x2 of data volume.

Create a reproducible issue in their github. The developer is very responsive.