網絡文件系統 S3QL 介紹

S3QL是一個使用一些網絡存儲服務如： Google Storage, Amazon S3 或 OpenStack來在線存儲數據的文件系統。S3QL有效地提供了一個動態，可以從任何能上網的電腦訪問無限容量的硬盤。

S3QL是一個符合標準，功能完整的UNIX文件系統與，任何本地文件系統的概念上沒有區別。此外，S3QL還支持一些額外的如功能，如壓縮，加密，刪除重復數據，和快照。這使得它特別適合在線備份和歸檔。

Features

• Transparency. Conceptually, S3QL is indistinguishable from a local file system. For example, it supports hardlinks, symlinks, ACLs and standard unix permissions, extended attributes and file sizes up to 2 TB.

• Dynamic Size. The size of an S3QL file system grows and shrinks dynamically as required.

• Compression. Before storage, all data may compressed with the LZMA, bzip2 or deflate (gzip) algorithm.

• Encryption. After compression (but before upload), all data can AES encrypted with a 256 bit key. An additional SHA256 HMAC checksum is used to protect the data against manipulation.

• Data De-duplication. If several files have identical contents, the redundant data will be stored only once. This works across all files stored in the file system, and also if only some parts of the files are identical while other parts differ.

• Immutable Trees. Directory trees can be made immutable, so that their contents can no longer be changed in any way whatsoever. This can be used to ensure that backups can not be modified after they have been made.

• Copy-on-Write/Snapshotting. S3QL can replicate entire directory trees without using any additional storage space. Only if one of the copies is modified, the part of the data that has been modified will take up additional storage space. This can be used to create intelligent snapshots that preserve the state of a directory at different points in time using a minimum amount of space.

• High Performance independent of network latency. All operations that do not write or read file contents (like creating directories or moving, renaming, and changing permissions of files and directories) are very fast because they are carried out without any network transactions. S3QL achieves this by saving the entire file and directory structure in a database. This database is locally cached and the remote copy updated asynchronously.

• Support for low bandwidth connections. S3QL splits file contents into smaller blocks and caches blocks locally. This minimizes both the number of network transactions required for reading and writing data, and the amount of data that has to be transferred when only parts of a file are read or written.

項目地址：http://code.google.com/p/s3ql/