Performance scenario RAM Disk and In memory database(IMDB)?

I w开发者_如何学Goas just wondering, we have in memory database(IMDB) and we also have a way to put the database in a RAM Disk. So which would be faster? You valuable comments and experiences

Wikipedia - Computer Data Storage

Latency The time it takes to access a particular location in storage. The relevant unit of measurement is typically nanosecond for primary storage, millisecond for secondary storage

It really depends on the hardware architecture. However internal memory is almost always the fastest way of storing and retrieving data, unless you have a specialized main board.