filesystems/s3backer 1.5.4_1 DragonFly

s3backer is a filesystem that contains a single file backed by the Amazon Simple Storage Service (Amazon S3). As a filesystem, it is very simple: it provides a single normal file having a fixed size. Underneath, the file is divided up into blocks, and the content of each block is stored in a unique Amazon S3 object. In other words, what s3backer provides is really more like an S3-backed virtual hard disk device, rather than a filesystem.

In typical usage, a normal filesystem is mounted on top of the file exported by the s3backer filesystem using a loopback mount (or disk image mount on Mac OS X).

By not attempting to implement a complete filesystem, which is a complex undertaking and difficult to get right, s3backer can stay very lightweight and simple. Only three HTTP operations are used: GET, PUT, and DELETE. All of the experience and knowledge about how to properly implement filesystems that already exists can be reused.

By utilizing existing filesystems atop s3backer, you get full UNIX filesystem semantics. Subtle bugs or missing functionality relating to hard links, extended attributes, POSIX locking, etc. are avoided.