MimdRAID: Low Latency Secondary Storage
Report ID: TR-612-99Author: Chen, Yuqun / Li, Kai / Yu, Xiang / Anderson, Thomas E. / Krishnamurthy, Arvind / Wang, Randolph Y.
Date: 1999-09-00
Pages: 16
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Abstract:
Disk arrays can provide scalable bandwidth with increasing number of disks, but they do not address latency. In this paper, we study how to improve secondary storage read latency by systematically increasing the ratio between disk heads and usable capacity. The most direct technique is to build ``faster" disks by altering disk geometry. In addition, as an alternative to building such disks, we also describe how we can emulate these faster disks using multiple conventional disks. We show that all these techniques are governed by a common principle that the overhead-independent part of the latency improves by a factor of the square root of the amount of extra resources. We evaluate some of these latency reduction techniques on a prototype implementation which we call MimdRAID. On a 12-disk system, for random reads, we achieve a 2x improvement in latency and 21x improvement in throughput compared to a single drive. This is 80% to 95% better than the throughput achieved on a conventional mirrored system.