Expressing File System Reorganization Policies with the ClassAd Language

In many modern file systems files must be periodically reorganized on disk in order to preserve disk space and provide for efficient I/O operation. Devising adaptive file system reorganization policies is a good first step towards increased flexibility, but does not achieve the goal of separating these policies from the underlying mechanisms of the operating system. The ClassAd language used to express resource allocation policies in the Condor distributed computing system is an excellent candidate for a file system policy description paradigm. A log structured file system (LFS) is an ideal environment for the use of ClassAds for file system reorganization policies. In this paper we explore using ClassAds to express file system reorganization policies in LFS, particularly cleaner policies.