The current GridStore has a read stream api, no write stream api (just a ad hoc special case with a file desctriptor) , and it's an old Stream (node.js <= 0.8).

It would be great to have:

1/ a write stream api that generalizes the writeFile() method

2/ a node.js 0.10 Readable & Writable Stream api (http://nodejs.org/api/stream.html#stream_api_for_stream_implementors)
With the new streams it's really easy to implement a Readable and a Writable stream, no need to hack around nasty bugs with pause() and resume(): we just have to implement _read() and _write().

The first point is really useful: currently we need to store the data in memory or disk before writing it into GridFS, this is a real issue when storing data from a large HTTP file upload for example.

The second point could simplify the implementation of the first point.

I understand we still need to keep compatibility with old node.js versions: we could keep the old code (with only a read stream) alongside the new one.

By the way: https://github.com/mongodb/node-mongodb-native/blob/V1.3.23/lib/mongodb/gridfs/gridstore.js#L321 :
numberOfChunksLeft is computed but never used in writeFile().