That's another way to do it - if you carve out a tmpfs large enough to support the shared memory file plus use swap on a less-than-fast SSD, you are basically letting the OS handle keeping the most relevant pieces in RAM. That's one way to do it. If you have fast enough disk storage already, it's unnecessary to do that. Another option is if your disk storage isn't fast enough by itself you can RAID two together (if available) to gain the performance needed.