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Is there any way we can figure out what all indexes are cached into RAM ? I want to know page related stats for individual indexes (# of hits and miss )

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You can get overall (instance wide) hit info from the db.serverStatus() command, and in particular:

http://docs.mongodb.org/manual/reference/command/serverStatus/#serverStatus.indexCounters.hits http://docs.mongodb.org/manual/reference/command/serverStatus/#serverStatus.indexCounters.misses

These numbers are totals seen for the lifetime of the process, so if you want to get a rate or see the trend over time, then you will need to record them periodically and diff the values accordingly. Thankfully, if you install MMS Monitoring, it will do that for you and graph the results.

However, there are currently no per-index statistics available. The relevant feature request can be found here for tracking and voting purposes:


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