US Patent 7870172 File system having a hybrid file system format

Embodiments of this invention disclose a file system having a hybrid file system format. The file system maintains certain data in two formats, thereby defining a hybrid file system format. In one exemplary application, the first format has properties favorable to write operations, e.g. a log-structured file system format, while the second format has properties favorable to read operations, e.g. an extent-based file system format. The data is stored in the first file system format and then asynchronously stored in the second file system format. The data stored in the second file system format are also updated asynchronously.