The Research And Implementation Of Energy-efficient RAID

In the last decades, parallel I/O systems are widely used in scientific and commercial fields. Large scale storage systems have increased total cost of data center while providing great storage capacity and performance. Most of the energy conservation technology tend to turn part of disks into low power state to reduce energy consumption, but didn't deal with the reliability and performance decrease.After investigating several energy conservation technologies,an new architecture that using sub-RAID as write buffer based on RAID10 is designed. Space that deserved from primary disks of RAID10 is organized as RAID5 which is used as a write buffer, while mirror disks are turned into low power state to conserve energy. In order to improve write performance, write requests are written to write buffer sequentially. When the mirror disks are in low power state, the system is still reliable because the write buffer is organized as a RAID5. As only little space is deserved from the primary disks, the storage space will not decrease much.An Energy conservation module is added in the bottom of IET to form an energy-efficient RAID. This module contains three smaller modules: request hander, disk controller and destager. Request hander is responsible to receive data from upper layer, and decides the position of data and redirects it to the right position. Disk controller is used to change disk states according to several conditions. Destager is activated when the space of write buffer is lower than threshold, and update data to primary disks and mirror disks.We evaluated our energy-efficient RAID by running some benchmarks and trace driven loads. The result show that our energy-efficient RAID can reduce 50% power cost than MD while keeping the same write performance. By test results and analysis, our energy-efficient RAID can reduce power cost obviously when the write requests are intensive.