Do you know of any resources that give some info on this topic in general? I've ...

kstirman · on March 19, 2013

from: http://docs.mongodb.org/manual/reference/server-status/

serverStatus.workingSet.pagesInMemory

pagesInMemory contains a count of the total number of pages accessed by mongod over the period displayed in overSeconds. The default page size is 4 kilobytes: to convert this value to the amount of data in memory multiply this value by 4 kilobytes.

If your total working set is less than the size of physical memory, over time the value of pagesInMemory will reflect your data size. Conversely, if your data set is greater than the size of the physical RAM, this number will reflect the total size of physical RAM.

Use pagesInMemory in conjunction with overSeconds to help estimate the actual size of the working set.

Also, there's a discussion of working set in this guide starting on page 9: http://info.10gen.com/rs/10gen/images/10gen-MongoDB_Operatio...

francesca · on March 19, 2013

this presentation offers a good overview pre 2.4, but will give you insights into how you can prepare for memory issues http://www.10gen.com/presentations/mongosv-2012/capacity-pla...