The core of information age is the information technology, piece the core of the information technology consists in the information process and storage. On with the rapid development of the information and the popularization of the personal computer, folk find information much and much useful and need it ever much than the past. Owning to the massive data, there is a immense challenge to the data storage technology. So how to save so galore documents and how to visit document as fast as possible become the key point. We cognize we need storage devices to save data, piece there are so galore kinds of storage devices and modes to save data. What's more, once saving the data and information, it is much important to ensure the storage safety as well as the accuracy, usability, dependability of data. Often, what is priceless is that invisible data.