S3QL is a file system that stores all its data online. It supports Amazon S3, Google Storage, and OpenStack and effectively provides you with a hard disk of dynamic, infinite capacity that can be accessed from any computer with Internet access. S3QL provides a standard, full featured Unix file system that is conceptually indistinguishable from any local file system. Additional features include compression, encryption, data de-duplication, immutable trees, and snapshotting, which make it especially suitable for online backup and archiving. The design favors simplicity and elegance over performance and feature-creep. Care has been taken to make the source code as readable and serviceable as possible. Solid error detection, error handling, and extensive automated test cases are provided.
storeBackup is a backup utility that stores files on other disks. It's able to compress data, and recognize copying and moving of files and directories (deduplication), and unifies the advantages of traditional full and incremental backups. It can handle big image files with block-wise changes efficiently. Depending on its contents, every file is stored only once on disk. Tools for analyzing backup data and restoring are provided. Once archived, files are accessible by mounting file systems (locally, or via Samba or NFS). It is easy to install and configure. Additional features are backup consistency checking, offline backups, and replication of backups.
The RAZip bitstream format was designed to provide a faster random access to compressed data than what is currently possible using the GZIP format. Its major features include fast random access to compressed data, freedom from patents, single-pass coding/decoding using a bounded amount of intermediate storage, the ability to choose from one of many algorithms for compression, encryption, or error correction, and comprehensive support for Unix file metadata, Macintosh file metadata, and arbitrary file metadata.
Shoelacer attempts to generate a pair of small C functions that compress or decompress a set of data (primarily short strings) presented to it, and possibly other data of that kind. The data it is given may consist of entries of just a few bytes or longer. Its goal is to be reasonably fast with a tiny memory overhead. Compression performance is not so much the goal, although it certainly isn't ignored.
pngcrush is an excellent batch-mode compression utility for PNG images. Depending on the application that created the original PNGs, it can improve the file size anywhere from a few percent to 40% or more (completely losslessly). The utility also allows specified PNG chunks (e.g. text comments) to be inserted or deleted, and it can fix incorrect gamma info written by Photoshop 5.0 as well as the erroneous iCCP chunk written by Photoshop 5.5.