A Reliable and Portable Multimedia File System Joo-Young Hwang, Jae-Kyoung Bae, Alexander Kirnasov, Min-Sung Jang, Ha-Yeong Kim Samsung Electronics, Suwon, Korea {jooyoung.hwang, jaekyoung.bae, a78.kirnasov}@samsung.com {minsung.jang, hayeong.kim}@samsung.com Abstract In this paper we describe design and imple- mentation of a database-assisted multimedia file system, named as XPRESS (eXtendible Portable Reliable Embedded Storage System). In XPRESS, conventional file system metadata like inodes, directories, and free space infor- mation are handled by transactional database, which guarantees metadata consistency against various kinds of system failures. File sys- tem implementation and upgrade are made easy because metadata scheme can be changed by modifying database schema. Moreover, us- ing well-defined database transaction program- ming interface, complex transactions like non- linear editing operations are developed easily. Since XPRESS runs in user level, it is portable to various OSes. XPRESS shows streaming performance competitive to Linux XFS real- time extension on Linux 2.6.12, which indi- cates the file system architecture can provide performance, maintainability, and reliability al- together. 1 Introduction Previously consumer electronics (CE) devices didn’t use disk drives, but these days disks are being used for various CE devices from per- sonal video recorder (PVR) to hand held cam- corders, portable media players, and mobile phones. File systems for such devices have re- quirements for multimedia extensions, reliabil- ity, portability and maintainability. Multimedia Extension Multimedia extensions required for CE devices are non-linear editing and advanced file indexing. As CE devices are being capable of capturing and storing A/V data, consumers want to personalize media data according to their preference. They make their own titles and shares with their friends via in- ternet. PVR users want to edit recorded streams to remove advertisement and uninterested por- tions. Non-linear editing system had been only necessary in the studio to produce broadcast contents but it will be necessary also for con- sumers. Multimedia file system for CE devices should support non-linear editing operations ef- ficiently. File system should support file index- ing by content-aware attributes, for example the director and actor/actress of a movie clip. Reliability On occurrence of system fail- ures(e.g. power failures, reset, and bad blocks), file system for CE devices should be recovered to a consistent state. Implementation of a reli- able file system from scratch or API extension to existing file system are difficult and requires long stabilization effort. In case of appending