Our current SSTable sizes are far greater than RAM. {150 Gigs of data, 32GB RAM}. Currently we run with mlockall and mmap_index_only options and don't experience swapping at all.

We use wide rows and size-tiered-compaction, so a given key will definitely be spread across multiple sstables. Will MMapping data files be detrimental for reads, in this case?

In general, when should we opt for MMap data files and what are the factors that need special attention when enabling the same?