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File access characterization and analysis of nonvolatile write caches
Abstract
The I/O subsystem of computer systems is becoming the bottleneck as a result of recent dramatic improvements in processor speed. Enhancing the performance of the disk and file system is becoming increasingly important to alleviate the effect of the I/O bottleneck. Disk and file system caches have been effective in closing the performance gap between the processor and the I/O subsystem. However, their benefit in commercial systems is restricted only to read operations as write operations are committed to disk to maintain consistency and to allow crash recovery. Consequently, write operations begin to dominate the traffic to the disk. Therefore, it has become increasingly important to address the performance of write operations. To modify an existing I/O subsystem or to architect a new one, it is important to understand the current file access patterns. Therefore, in the first part of the dissertation we provide a comprehensive analysis of several file I/O traces collected at commercial, production computer systems. Next, we investigate the use of non-volatile disk caches to address the write I/O bottleneck problem. The non-volatile caches can be easily incorporated into an existing file system. We address the issues around managing such a cache using a detailed trace driven simulation. We propose cache management policies that reduce the number of disk writes to a small fraction of the total number of application write operations. Our schemes also improve the write response time by cleaning the write cache asynchronously when the disk is idle and by piggybacking dirty blocks on disk read operations. Finally, we extend the use of non-volatile write caches to the distributed file system environment. We develop a synthetic file access workload model based on the I/O traces and use it to evaluate alternative write caching policies. We show that small non-volatile caches at both the clients and at the server is quite effective. They reduce the write response time and the load on the file server, thus improving the performance and scalability of the system.
Subject Area
Computer science|Electrical engineering
Recommended Citation
Biswas, Prabuddha, "File access characterization and analysis of nonvolatile write caches" (1993). Doctoral Dissertations Available from Proquest. AAI9329571.
https://scholarworks.umass.edu/dissertations/AAI9329571