DATE: Monday, June 25, 2007 -- NOTE SPECIAL DAY
TIME: 12:00 pm - 1:00 pm

Dushyanth Narayanan
Microsoft Research Cambridge

Write Off-loading: Practical Power Management for Data Center Storage

In data centers of all sizes power usage is a problem impacting server density and 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 server workloads make spinning disks down ineffective: idle periods are too short. We propose changing the block-level access pattern for storage systems, using {\em write off-loading}. Off-loading allows block-level writes on one volume to be temporarily redirected to another volume in the data center. This creates significant periods when disks can be spun down.

The key challenges are doing this transparently and efficiently at the block level, and achieving consistency in the presence of failures. Consistency is challenging because each write off-load can use any available volume, and must be recoverable from these despite failures.

I will describe the rationale and design of our write off-loading clients and servers; and also describe the real-world block-level traces from data centers that we use to validate the design. I will present some preliminary results on the performance and energy savings of write off-loading, based on replaying these traces on a small experimental testbed representing a single rack in a data center.

Dushyanth Narayanan has been a researcher at Microsoft Research, Cambridge, UK, since finishing his Ph.D. at CMU-CS in 2002. His research interests are operating systems, distributed systems, performance measurement and modelling, and mobile computing. His most recent focus has been data center management, specifically power management.

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