Lucent Technologies Inc.

Sun Microsystems, Inc.

Christopher Stein

Eran Gabber

John H Howard

Elizabeth A Shriver

Lan Huang

A special-purpose file system is provided which includes a combination of services and features which improve the performance of applications employing caches, such as caching web proxies. This file system also provides a file system cache which can be used as a general high-performance file system cache for file systems which need a cache. The services and features include collocating files together on a disk; keeping file meta-data in memory; compressing file names to hash values for reference; using a flat naming scheme for files; providing background daemons that pack files into clusters and clean disk and main memory space; and implementing a user-level library. The file system reduces access to related disk files, eliminates disk operations that are needed to maintain directory and meta-data information, and avoids multiple buffering of file data, and saves and efficiently manages disk and main memory space.

File system for caching web proxies

A data storage system includes a computer coupled to a non-volatile storage, such as a disk drive. The computer includes a block cache for storing cached copies of data blocks, and a hash table that stores hash values corresponding to the data blocks. Prior to writing back a modified cache block to the non-volatile storage, a log recorder of the computer stores an updated hash value corresponding to the modified cache block within a write-ahead hash log, which is also contained in non-volatile storage. The log recorder creates a log record including an updated hash value and an address corresponding to a modified cache block. The log recorder additionally maintains a first pointer value indicative of log records that have been stored to the write-ahead hash log, and a second pointer value indicative of the most recent log record stored in the write-ahead hash log for which a corresponding modified cache block has been stored to the non-volatile storage. These pointer values are stored in the write ahead hash log with the log records. Log records are grouped into log blocks which are eventually written to the non-volatile storage as a group. After the log record containing the updated hash value has been successfully written to write-ahead hash log, a cache manager initiates the write-back of the dirty data block to the non-volatile storage.

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Cambridge, MA, United States of America

Christopher Stein