A system for efficient backups using dynamically shared storage pools in peer-to-peer networks comprises one or more processors and memory coupled to the processors. The memory stores instructions executable by the processors to implement a backup manager configured to dynamically subdivide a storage pool into one or more portions of storage currently designated for local backup data and one or more portions of storage currently designated for peer-to-peer (P2P) backup data. In response to local backup data received from a backup client, the backup manager may store the local backup data in a portion of the storage pool that is currently designated for local backup data. The backup manager may then generate a P2P version of the local backup data, e.g., by encrypting and/or redundancy encoding the local backup data, and transmit parts of the P2P version to each of one or more peer devices in the P2P network.