SnapShot

A faster and more popular approach to snapshots is COW, also called "pointer snapshots." A pointer snapshot does not copy data. Instead, it simply records an index of data locations on the volume being protected. This requires far less storage space then a full copy. In most cases, the storage space allocated for a snapshot volume is only about 30% of the data volume being protected. "There's nothing in it [the snapshot volume] other than some system-oriented metadata that the system needs to manage this whole environment," says Arun Taneja, consulting analyst and founder of the Taneja Group. For example, it would take up to about 30 GB to protect 100 GB of primary storage, bringing the total storage needs to 130 GB. Low storage demands also mean that pointer snapshots are quite fast, so the production network is not interrupted for more than just a few seconds. This combination of low storage requirements and fast performance make pointer snapshots ideally suited for frequent use, allowing for low RPO.