My forum uses IP.Board but it's pretty slow, so I'm planning to change it to NodeBB.

But my question is: I know that Redis is ultra fast since it uses RAM, but my forum is huuuuuge: 6.5 million posts and 31.200 members.

My server is CentOS one and has 32Gb of memory ram. Will it be too much for Redis? Should I consider to use MongoDB instead?