Meeting most of the requirements on that list, I have found Arq[1] to be a great backup solution on OS X. It stores encrypted, incremental backups on S3 and alt

Meeting most of the requirements on that list, I have found Arq[1] to be a great backup solution on OS X. It stores encrypted, incremental backups on S3 and although the client itself isn't open source, the data format is[2]. The company also maintains an open source recovery tool[3]. The only requirement that isn't met is cost, because S3 costs about $60/yr for 50GB. [1] http://www.haystacksoftware.com/arq/index.php http://www.haystacksoftware.com/arq/index.php [2] http://www.haystacksoftware.com/arq/s3_data_format.txt http://www.haystacksoftware.com/arq/s3_data_format.txt [3] http://sreitshamer.github.io/arq_restore/ http://sreitshamer.github.io/arq_restore/