Various organizations face an explosive growth of data that must be protected and backed up. This challenge is made more difficult by the movement from stand-alone server backup to backup over the local area network (LAN) and by the need to automatically manage multiple backup servers efficiently for concurrent backup jobs. In this paper, we present a novel software approach to backup service, where application servers provide their unused resources to participate in a virtual backup environment. We implement a prototype with the following desirable features: single-instance storage to save storage and communication costs, data replication to enhance data availability, data redirection to avoid job resubmission, and intelligent scheduling to achieve workload balance. The experimental study shows that our approach is promising.