Electric energy consumed in data centers is rapidly growing. Power-aware IT, recently called `green IT', is widely recognized as a significant challenge. Disk storage is a non-negligible energy consumer. Rather, in light of recent data-intensive systems where a number of disk drives are incorporated, the disk storage may be what we must consider primarily. Yet, all of the disk drives are not used for primary datasets, but rather larger portion of them are utilized for storing a variety of copies such as backups and snapshots. Saving the energy of such storage resources that manage copies is a promising approach. The paper presents a power-aware disaster recovery system, in which the reflection of transferred updated information can be deferred through eager compaction technique. Great energy saving of storage systems is expected in the remote secondary site. Our experiments using a commercial database system show that 80-85% energy of the secondary-site disk storage can be saved ...