Evaluating Delayed Write in a Multilevel Caching File System

Delayed write in a multilevel file system cache hierarchy offers a way to improve performance in diverse client/server scenarios, such as integrating mass store into a distributed file system or providing distributed file system access over low-speed links. Using file system traces and cache simulations, we explore extensions and modifications to the traditional client caching model employed in such file systems as AFS, Sprite, and DFS. High cache hit rates at an intermediate cache server—a machine logically interposed between clients and servers that provides cached file service to the clients—combined with high client cache hit rates lend practicality to an integrated mass storage file system. In such a system, magnetic tape or optical-based mass storage devices may be used as a first-class data repository, fronted by disk and RAM caches to offer acceptable access times to the large, but slow, mass storage system. Similarly, a high cache hit rate is necessary for users accessing file systems via low-speed links, where a delayed write intermediate caching server can mediate traffic to make better use of available bandwidth. In an example taken from mobile computing, an intermediate server might be used as a docking station at a user's home. This arrangement would be convenient for users of mobile computers who upload large amounts of data generated while operating in disconnected mode. Simulations of delayed write caching strategies are applicable to both the mass storage and low-speed link scenarios.http://deepblue.lib.umich.edu/bitstream/2027.42/107940/1/citi-tr-95-9.pd

Building regulatory compliant storage systems

In the past decade, informational records have become entirely digital. These include financial statements, health care records, student records, private consumer information and other sensitive data. Because of the delicate nature of the data these records contain, Congress and the courts have begun to recognize the importance of properly storing and securing electronic records. Examples of legislation in-clude the Health Insurance Portability and Accountabilit

A Cached WORM File System

This paper describes a general-purpose file system that uses a write-once-read-many (WORM) optical disk accessed via a magnetic disk cache. The cache enables blocks to be modified a number of times before they are written to the WORM and increases performance. Snapshots of the file system can be made at any time without limiting the users' access to files. These snapshots reside entirely on the WORM, are accessible to the user via a second read-only file system, do not contain multiple copies of unchanged data, and can be used to rebuild the file system in the event that the disk cache is destroye