File sync application like dropbox for Amazon S3

I'm struggling with a bit problem. I have the past days been thinking about how nice it would be with a dropbox kind of app that could keep a folder synched with my amazon s3 back end. Sadly, not really tried alot out, but from reading i havent been able to find any apps that features exactly what dropbox do.

I dont wanna mount a network drive and such.

I'm quite sure that i would be able to write a little app myself that could upload and download files from amazon s3 bucket, but thinking about it lead me to a dilemma.

From my understanding dropbox does like svn do, it only commit its changes. So are anyone able to give some input on the stuff behind the scene?

If i change a file on my 开发者_如何学编程system, how can it check the changes vs this file and the one on the remote site without first downloading the remote file?

If anyone know of a client that works great and like dropbox, feel free to share aswell. I found that ubuntu one have a great system working with cheaper prices then dropbox.

Unfortunately I am not allowed to talk about my client here, but I can tell you two things. First, it is not at all easy to make a dropbox like app, it will take months to make something decent. Second, you can use the object Etag to see if it has changed locally. Etag is basically a checksum and you can easily calculate it on the client.

I built something similar after seeing this question. This is not THE solution, but a good place to start

http://sharathprabhal.tumblr.com/post/68737134239/an-auto-syncing-nobackend-cloud-storage-app-using-only

https://github.com/sharathprabhal/NBS3Sync

This is an incredibly old question, but S3FS + rsync is a perfect replacement for dropbox. I'm making an assumption that you have the skill to setup a fuse based filesystem on Linux.