Speaking of on-line/cloud storage... Wuala

[richard.pieri-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org (Richard Pieri)]

On Apr 23, 2011, at 11:34 AM, Hsuan-Yeh Chang wrote:
> 
> Just out of curiosity, how does cloud storage like Wuala and Dropbox works?  Do 
> they just put your files on the server (like googledoc) and provide a convenient 
> user interface, or do they make copies (i.e., sync) of files in each device?

The simple answer to the question is that both use local copies for storage.  These are not network file systems like NFS or AFS.

Dropbox works a lot like rsync or Unison.  It has a directory that it monitors for changes.  Any changes are synchronized with an Amazon S3 bucket.  Any changes to that bucket are mirrored to other Dropbox clients on the same account.

Wuala works a little differently.  It creates a Cryptree file system and mounts it like a removable drive via FUSE (Linux, Mac) or CBFS (Windows).  Changes to the FUSE/CBFS are encrypted and chunked, and these chunks are sent first to the Wuala storage servers in Europe and second to the Wuala cloud.  This cloud is composed of other Wuala clients trading storage.  Changes to the Cryptree are downloaded by other Wuala clients on the same account.

Wuala layers automated backups and sync on top of the mounted Cryptree so there is a greater local storage overhead with Wuala if you use these features.  On the other hand, Wuala offers substantially better privacy and security than Dropbox.

--Rich P.