mongodb creates 80+ files 2GB each while database is empty

Question

Background:

I set the replicaSet and initiated 3 instances (1 arbiterOnly) of mongod on localhost using different ports.

I haven noticed tha

Answer 1

It sounds like it's preallocating space for the oplog. The oplog is allocated regardless of what you have inserted into the database http://www.mongodb.org/display/DOCS/Excessive+Disk+Space:

The replication oplog is preallocated as a capped collection in the local database.

The default allocation is approximately 5% of disk space (64 bit installations).

If you would like a smaller oplog size use the --oplogSize command line parameter.

Answer 2

There are various command line parameters I have found to reduce the size of the empty database.

Already mentioned:

--oplogSize <value>

Also:

--smallfiles
--nssize <value>

The combination of all 3 parameters makes for an 18mb empty database (tested against MongoDB 64bit, Windows 7).

http://docs.mongodb.org/manual/reference/program/mongod/