By default Sophia uses pread(2) to read data from disk. Using mmap mode, Sophia handles all requests by directly accessing memory-mapped node files memory.
Following variable can be set to enable or disable mmap mode: db.database_name.mmap
sp_setint(env, "db.test.mmap", 1);
It is a good idea to try this mode, even if your dataset is rather small or you need to handle a large ratio of read request with a predictable pattern.
Disadvantage of mmap mode, in comparison to RAM Storage, is a possible unpredictable latency behaviour and a OS cache warmup period after recovery.