Data protection method and device

The present invention provides a data protection method, including: setting LUN critical section; when data of the critical section changed, acquiring data variation; judging the data variation whether exceeding a default threshold or not, if the data variation exceeding the default threshold, starting snapshot. The invention also provides a data protector and a storage device of the data protector. The embodiment of the invetion divides part content in LUN into LUN critical section, starting quantitative tactics aiming at the critical section, in other words, snapshot is started only when the data variation exceeding the default threshold, when non-changing or changing lesser data in the critical section, the snapshot is not started to avoid wasting of resources.