How to determine the RAM Size of my MongoDB Sever -

i have used command

db.collection.stats()  db.stats() {         "collections" : 17,         "objects" : 487747,         "avgobjsize" : 1924.9327048654322,         "datasize" : 938880152,         "storagesize" : 1159314432,         "numextents" : 82,         "indexes" : 32,         "indexsize" : 153812992,         "filesize" : 8519680000,         "ok" : 1 } 

from net found out statement

indexes should in memory .(which nothing ram)

the index size 153812992 , datasize 938880152

could please tell me amount of ram require on mongodb server , performance aways great .

as per applciation design , daiily 100k insertions/updations might happen , , 1 more question have , index size grow each day ??

then in case how can determine best fit ram size application .

please advice , in advance .

there tool in later versions of mongodb finding out how big working set is, still quite experimental should work: http://docs.mongodb.org/manual/reference/command/serverstatus/#serverstatus.workingset

the best way use make automated test script use application , in meantime print out serverstatus , archive value of working set document. can graph it, etc etc , come reasonable conclusion of ram needs be.