What we are doing:
1. We have several web servers
2. We are uploading some big file (e.g. 100Mb)
3. The file is chunked on the client-side (e.g. by plupload, etc)
4. We are using MongoDB GridFS to store uploaded files.

What problems we have:
1. There is no possibility to append the next uploaded chunk to the already stored in DB.
2. Also we can't store glue the chunks on a web server before saving into DB, because each file chunk is sended by load balancer to an unpredictable web server. So chunks are uploaded to different web servers.

What the purpose is:
1. Implement a new method appendBytes(id, bytes)
2. Implement a new method appendFile(id, filename)