The energy consumption of disks is a growing concern. It now contributes 27% to the operating costs for data centers. Unfortunately, existing RAIDs are not designed to conserve energy. This is, due to uniform striping in which even light loads generate activities on all drives.

By introducing a skewed striping pattern, PARAID can be “gear shifted” to a minimum striping level so the performance matches the load. Unused disks are powered down. Based on our “2-gear” prototype, PARAID consumes 15% less power than a traditional RAID, while not compromising performance.

We propose Power-Aware RAID (PARAID), which implements a skewed striping strategy to achieve power savings without performance degradation. By assigning data blocks in a skewed pattern, the number of powered-on disks can vary according to the demands placed on the system.

Click here to go to the PARAID webpage.

The rapidly declining cost of persistent RAM technologies prompts the question of when, not whether, such memory will become the preferred storage medium for many computers. In anticipation of that development, we present Conquest, a file system that provides a transition from disk to persistent RAM as the primary storage medium. Conquest is incrementally deployable and realizes most of the benefits of persistent RAM as it becomes cheaply abundant. As of October 2001, Conquest can be used effectively for a hardware cost of below $200.

We compare Conquest's performance to ext2, reiserfs, SGI XFS, and ramfs, using popular benchmarks. Our measurements show that Conquest incurs little overhead compared to ramfs. Compared to disk-based file systems, Conquest achieves 24% to 1900% faster performance for working sets that fit in memory, and 43% to 96% faster performance with working sets larger than the memory size.

Click here to go to the CONQUEST webpage.