Ugarit is a backup/archival system based around content-addressible storage. Learn more...


Development priorities are: Performance, better error handling, and fixing bugs! After I've cleaned house a little, I'll be focussing on replicated backend storage (ticket [f1f2ce8cdc]), as I now have a cluster of storage devices at home.



The Ugarit implementation contained herein is the work of Alaric Snell-Pym and Christian Kellermann, with advice, ideas, encouragement and guidance from many.

The original idea came from Venti, a content-addressed storage system from Plan 9. Venti is usable directly by user applications, and is also integrated with the Fossil filesystem to support snapshotting the status of a Fossil filesystem. Fossil allows references to either be to a block number on the Fossil partition or to a Venti key; so when a filesystem has been snapshotted, all it now contains is a "root directory" pointer into the Venti archive, and any files modified therafter are copied-on-write into Fossil where they may be modified until the next snapshot.

We're nowhere near that exciting yet, but using FUSE, we might be able to do something similar, which might be fun. However, Venti inspired me when I read about it years ago; it showed me how elegant content-addressed storage is. Finding out that the Git version control system used the same basic tricks really just confirmed this for me.

Also, I'd like to tip my hat to Duplicity. With the changing economics of storage presented by services like Amazon S3 and, I looked to Duplicity as it provided both SFTP and S3 backends. However, it worked in terms of full and incremental backups, a model that I think made sense for magnetic tapes, but loses out to content-addressed snapshots when you have random-access media. Duplicity inspired me by its adoption of multiple backends, the very backends I want to use, but I still hungered for a content-addressed snapshot store.

I'd also like to tip my hat to Box Backup. I've only used it a little, because it requires a special server to manage the storage (and I want to get my backups *off* of my servers), but it also inspires me with directions I'd like to take Ugarit. It's much more aware of real-time access to random-access storage than Duplicity, and has a very interesting continuous background incremental backup mode, moving away from the tape-based paradigm of backups as something you do on a special day of the week, like some kind of religious observance. I hope the author Ben, who is a good friend of mine, won't mind me plundering his source code for details on how to request real-time notification of changes from the filesystem, and how to read and write extended attributes!

Moving on from the world of backup, I'd like to thank the Chicken Team for producing Chicken Scheme. Felix and the community at #chicken on Freenode have particularly inspired me with their can-do attitudes to combining programming-language elegance and pragmatic engineering - two things many would think un-unitable enemies. Of course, they didn't do it all themselves - R5RS Scheme and the SRFIs provided a solid foundation to build on, and there's a cast of many more in the Chicken community, working on other bits of Chicken or just egging everyone on. And I can't not thank Henry Baker for writing the seminal paper on the technique Chicken uses to implement full tail-calling Scheme with cheap continuations on top of C; Henry already had my admiration for his work on combining elegance and pragmatism in linear logic. Why doesn't he return my calls? I even sent flowers.

A special thanks should go to Christian Kellermann for porting Ugarit to use Chicken 4 modules, too, which was otherwise a big bottleneck to development, as I was stuck on Chicken 3 for some time! And to Andy Bennett for many insightful conversations about future directions.

Thanks to the early adopters who brought me useful feedback, too!

And I'd like to thank my wife for putting up with me spending several evenings and weekends and holiday days working on this thing...

Version history