White Papers, etc

posted on 23 July 2008 08:25

Here is the abstract from a Microsoft research paper entitled 'Write Off-Loading: Practical Power Management for Enterprise Storage':

In enterprise data centers power usage is a problem impacting server density and the total cost of ownership. Storage uses a significant fraction of the power budget and there are no widely deployed power-saving solutions for enterprise storage systems. The traditional view is that enterprise workloads make spinning disks down ineffective because idle periods are too short. We analyzed block-level traces from 36 volumes in an enterprise data center for one week and concluded that significant idle periods exist, and that they can be further increased by modifying the read/write patterns using write off-loading. Write off-loading allows write requests on spun-down disks to be temporarily redirected to persistent storage elsewhere in the data center.

The key challenge is doing this transparently and efficiently at the block level, without sacrificing consistency or failure resilience. We describe our write offloading design and implementation that achieves these goals. We evaluate it by replaying portions of our traces on a rack-based testbed. Results show that just spinning disks down when idle saves 28–36% of energy, and write off-loading further increases the savings to 45–60%.

This sounds interesting; a version of spin down for enterprise drives. Robin Harris unearthed this by the way. The comments to his piece make interesting reading, particularly one saying this technique may not be useful for SANs.

Download the paper below.

^{[B&F staff.]}

Download file: Write Off-Loading paper 23 JUly 08.pdf