Hello,
First there is know issue in ruby library. That a look on this post
http://s3sync.net/forum/index.php?topic=191.0Second and more important. Given that S3 is all or nothing, i.e. if you want to change a file you have to PUT the whole thing again.
When using s3sync every time a local file has been changed it will uploads the hole new file, not just what has changed. That means that are wasting unnecessary bandwidth and take more time.
If you to benefit from Rsync bandwidth efficient algorithm You need to use your own Amazon Ec2 machine or to
3rd party gateway like:
http://www.s3rsync.com/Danm