For starters, I use and love Dropbox. It is one of, if not THE, best file synchronization tool I have used or know of. I’m going to make the claim that no open-source Dropbox clone comes close to its functionality at the moment. But first, here is a list of the requirements for my personal file synchronization utility which Dropbox satisfies:

1. a) It must keep a version-controlled copy of all of the files I am synchronizing. b) I should be able to easily revert to an earlier version of a file if I wish, independently of the state of the version of the rest of my files.
2. It must work automatically and behind-the-scenes to keep my files in sync. I don’t want to have to think about synchronization or backups -that should be handled for me.
3. File synchronization should begin as soon as I save the file locally. If I update a file I’m sharing with a friend, I want them to get the new version as soon as possible, which brings me to…
4. Sharing files with others should be easy and intuitive.
5. It should have an easy-to-use API which makes it easy for others to build applications around.
6. My files must be accessible on my local machine, even if I am disconnected from the Internet.

With all of the above compliments, why would I want to replace Dropbox? Well, even Dropbox isn’t perfect, and I have a few additional requirements my ideal personal synchronization tool would meet:

1. A high level of privacy and security. Although Dropbox claims to keep your files private and secure, there have been a few cases where that seems to be wearing thin. Many people are searching for a replacement. It seems to me that encrypting files locally before transmission (and not storing the private key anywhere except locally) is a good solution.
2. I should be able to control where my files are stored. This probably doesn’t matter for your average user, but as a superuser, I want control. I.e., I should be able to setup my own server and store my files there if I want. This also means my available storage space is only limited by the size of my hard drive. Although related with privacy and security, I think this warrants a separate mention.
3. The ability to share a public link with people who don’t have Dropbox accounts. This would make file sharing much easier. (A shout out to Spence for this idea)
4. A proper access control facility. This would probably ideally mirror Unix-like ACLs.
5. I should be able to revert all my files to a certain point in time. This is not (I don’t think) currently an option with Dropbox.
6. Finally, it should be open source for the usual reasons.

Existing “Solutions”

Looking at the set of above requirements, it becomes clear that a) I am very picky, and b) there is no existing solution which can satisfy all of my requirements. There are a great number of open-source Dropbox clones out there. Below is a partial list of what I see as the major competitors in this space, along with their shortcomings on the above items. Feel free to leave a comment if I have missed one, or made false claims about one I have listed.

• SparkleShare – It’s based on git. Git is fantastic, but not for all the image and music files I want to sync. You’re limited to storing your files in a git repository.
• ownCloud – No client synchronization tool. They tell  you to use use WebDAV (see below).
• Syncany – Doesn’t support sharing files with others.
• duplicity – Only synchronizes when you tell it to.
• NFS and WebDAV – No access to files when you are offline. This is a must.

What’s Next?

After searching for a synchronization client which meets my requirements and failing, I did what every self-respecting techno-geek would do, and began writing my own. I know I will catch some grief for starting yet another project and not contributing to an existing one, but I believe that the above projects all have core design limitations which will inhibit them from meeting all of the above without changing key components of their infrastructure.

I am aiming to eventually hit all of the above requirements. In the first pass, I am aiming to meet Dropbox requirements numbers 1.a., 2, 3, 6 and non-Dropbox requirements 2 and 6. These are, in my opinion, the subset of the above requirements that is in the middle of the Venn Diagram containing easy-to-implement features on the one side and important features on the other.

For the moment, I am calling my project “Asink” for both the asynchronous method of file synchronization, the fact that it aims to be a sink for all of my data, and that I should be able to store everything and the kitchen sink in it. You can follow my development on github at http://github.com/aclindsa/asink. I am planning to write another post to explain my initial design decisions, as well as an update as soon as I have a version with the basic functionality properly working (hopefully within the next week).

Feel free to let me know what you think in the comments.