MongoDB: Sharding on single machine. Does it make sense?

created a collection in MongoDB consisting of 11446615 documents.

Each document has the following form:

{ 
 "_id" : ObjectId("4e03dec7c3c365f574820835"), 
 "httpReferer" : "http://www.somewebsite.pl/art.php?id=13321&b=1", 
 "words" : ["SEX", "DRUGS", "ROCKNROLL", "WHATEVER"],     
 "howMany" : 3 
}

httpReferer: just an url

words: words parsed from the url above. Size of the list is between 15 and 90.

I am planning to use this database to obtain list of webpages which have similar content.

I 'll by querying this collection using words field so I created (or rather started creating) index on this field:

db.my_coll.ensureIndex({words: 1})

Creating this collection takes very long time. I tried two approaches (tests below were done on my laptop):

1. Inserting and indexing Inserting took 5.5 hours mainly due to cpu intensive preprocessing of data. Indexing took 30 hours.
2. Indexing before inserting It would take a few days to insert all data to collection.

My main focus it to decrease time of generating the collection. I don't need replication (at least for now). Querying also doesn't have to be light-fast.

Now, time for a question:

I have only one machine with one disk were I can run my app. Does it make sense to run more than one instance of the database and split my data between them?