The easy solution would be to use something like Amazon S3 to store documents as objects and let them worry about backup; but governments are worried (and right

The easy solution would be to use something like Amazon S3 to store documents as objects and let them worry about backup; but governments are worried (and rightly so) about the US government spying on them. Thus, the not-so-easy-but-arguably-better solution would be to self-host an open source S3-compatible object storage solution. Are there any good open source alternatives to S3?