50GB local database on replica set creation

Does anyone have any idea why the local database can be at 50GB before I even created my first database in a brand new replica set? I mean, 50GB seems like a lot for a replica set without any databases.



That is the preallocation of the oplog which is required for replica set operation.

http://docs.mongodb.org/manual/core/replica-set-oplog/
For 64-bit Linux, Solaris, FreeBSD, and Windows systems, MongoDB allocates 5% of the available free disk space, but will always allocate at least 1 gigabyte and never more than 50 gigabytes.

Thanks for the info, Daniel.



If you specify --oplogSize XXX <- number in Megabytes how big the oplog should be.