mongoDB gridfs and sharding

If you want use gridfs and sharding chunks. In example is the mistake. Sharding by "_id" dosen't work.

Working example.

First ....
http://www.mongodb.org/display/DOCS/A+Sample+Configuration+Session

and then ...
$mongo
> use admin
switched to db admin
> db.runCommand( { shardcollection : "test.dexters.chunks", key : { n : 1 } } )
{"collectionsharded" : "test.dexters.chunks" , "ok" : 1}

$vim test_load.py
====================================================
#!/usr/bin/env python
import sys
import os.path
from pymongo.connection import Connection
from gridfs import GridFS

connection = Connection("localhost", 27017)
db = connection["test"]

name = os.path.basename(sys.argv[1])

fs = GridFS(db)
fp = fs.open(name, 'w', 'dexters')

for l in open(sys.argv[1]):
    fp.write(l)
fp.close()
====================================================

There is at leas two sharding strategy, by file_id or by (n, id).
Sharding by file_id is no RAID or RAID-1 (on file level) sharding by n when you use many servers can be like (RAID-0, RAID-10). On collection level performance is always RAID-0, RAID-10 ;-)