Soft Updates: A Solution to the Metadata Update Problem in File Systems

摘要

Metadata updates, such as file creation and block allocation, have consistently been identified as a source of performance, integrity, security, and availability problems for file systems. Soft updates is an implementation technique for low-cost sequencing of fine-grained updates to write-back cache blocks. Using soft updates to track and enforce metadata update dependen- cies, a file system can safely sue delayed writes for almost all file operations. This article describes soft updates, their incorporation into the 4.4 CSD fast file system, and the resulting effects on the system.