Question

I’m trying MongoDB but I don’t understand the files created by it.

If I create a document on my db collection lets say users, it will create these files on my /data/db/

_tmp (folder)
mongod.lock
users.0 - 16.8MB
users.1 - 33.6MB
users.ns - 16.8MB

I’ve added some documents and the files size haven’t changed..I’m a bit lost here…does anyone know how those files work? I’ve tried to open them with gedit/vim and nothing.

Thanks in advance for any help.

Answer 1

The .0, .1 files are datafiles. Each datafile is preallocated to a particular size. (This is done to prevent file system fragmentation, among other reasons.) The first filename for a database is .0, then .1, etc. .0 will be 64MB, .1 128MB, et cetera, up to 2GB. Once the files reach 2GB in size, each successive file is also 2GB.
Information regarding datafiles can be found here:

http://www.mongodb.org/display/DOCS/Excessive+Disk+Space

The “.ns” files are namespace files. Each collection and index would count as a namespace. Each namespace is 628 bytes, the .ns file is 16MB by default.

Thus if every collection had one index, we can create up to 12,000 collections. The –nssize parameter allows you to increase this limit.

Maximum .ns file size is 2GB.