Yes, but it should be noted that to see this speed up you can only do read caching. You can do write buffering in RAM but you need to mirror it to another node or you risk data loss in a power outage situation. RAM-over-network is roughly equivalent to SSD performance. It should also be noted that not all SSDs are created equal. You can get an SSD that will do tens of thousands of IOPS or you can get SSDs that do over a million IOPs per drive.