We propose a scheme for improving write performance in traditional mirrored disks using write caching. The technique uses write-only disk caches to improve write performance; a write through to disk for cached data and a write twice scheme to provide a highly fault tolerant system. The scheme is simple and can be readily integrated into existing systems with only low-level software redesign. Unlike some mirroring techniques, this technique maintains the semantics of traditional mirroring, allowing a disk to disk copy during recovery while improving write efficiency by almost a factor of 2 over traditional mirrors.
