Carnegie
Mellon University School of Computer Science Tecnical Report CMU-CS-03-192,
October, 2003. Superceded by Proceedings of the 3rd USENIX Conference
on File and Storage Technologies (FAST '04). San Francisco, CA.
March 31, 2004.
Eno Thereska, Jiri Schindler, John Bucy, Brandon Salmon, Christopher R. Lumb, Gregory R. Ganger
Electrical and Computer Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
This paper describes a programming model and system support for clean construction of disk maintenance applications. Such applications expose the disk activity to be done, and then process completed requests as they are reported. The system ensures that these applications make steady forward progress without competing for disk access with a system’s primary applications. It opportunistically completes maintenance requests by using disk idle time and free-block scheduling. In this paper, three disk maintenance applications (backup, write-back cache destaging, and disk layout reorganization) are adapted to the system support and evaluated on a FreeBSD implementation. All are shown to successfully execute in busy systems with minimal (e.g., <2%) impact on foreground disk performance. In fact, by modifying FreeBSD’s cache to write dirty blocks for free, the average read cache miss response time is decreased by 15–30%.
Keywords: scheduling, disks, asynchronous, interfaces
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