Prof. Dr. Frank Bellosa, Andreas Merkel

Abstract: 

Because of the rising energy costs and the increased energy consumption of computer systems it is becoming more and more important to increase energy efficiency. To achieve this modern operating systems use several power management strategies which mostly focus on reducing the energy consumption of the CPU. Other components like hard disk drives are often neglected and are at best just turned off if not needed.

To also increase the energy efficiency of systems where the disk drives are not idle long enough to be turned off, we propose to utilize compression to reduce disk activity. Due to compression more data can be stored in caches in main memory and thus the disk has to be accessed less often, and reading or writing the compressed data from disk takes less time and therefor less energy.

To evaluate if the energy saved by the disk drive outweighs the additional energy needed by the CPU for compression and decompression we implement a block device driver that transparently compresses all data written to disk. The results of our measurements show that on desktop systems, where the CPU consumes significantely more energy than the disk drive, no energy can be saved using this approach. On embedded systems and mobile devices though, where the CPU and the disk energy consumption are similar, it is possible to improve energy efficiency by upto 50% while at the same time also increasing I/O performance.

BibTex: 

@studythesis{koller08filecompression,
  author = {Clemens Koller},
  title = {Improving Energy Efficiency Through File Compression},
  type = {Study Thesis},
  address = {System Architecture Group, University of Karlsruhe, Germany},
  month = jun # "~3",
  year = 2008
}