Does running MongoDB in-memory create duplicates on RAM

Question

You can create ramdisks, tmpfs etc on RAM to create partitions to be used for different applications.

A similar one was posted in the following post: How to use MongoDB as a pure in-memory DB (Redis style)

MongoDB uses the resident memory for the hot data.

Hence 1) Does using ramdisk duplicate the ram usage for the same data?

2) Is there a way to disable the usage of resident memory?

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Edit : We can think of the hosting OS as CentOS or Ubuntu Servers, since they are the foremost used servers.

Answer 1

By the way MongoDB introduced plug-able storage engines in 3.0 release. And it ships with an experimental in-memory DB storage engine.

I was planning to use in memory DB for our testing environments, in order to get fast responses. So being experimental seems fine to me.

http://www.mongodb.com/blog/post/whats-new-mongodb-30-part-3-performance-efficiency-gains-new-storage-architecture