Data storage principle
As we know, a brand new hard disk can not be used unless we partition it. After partitioning hard disk, we need to format partition. Formatting programs will divide the partition into catalogue file allocation area and data storage area. When we store files to hard disk, system will firstly write file name and file size to file allocation table, and then go on writing information about starting place of the data. Next, system will write real data to data area. After these operations, data storage is finished.
Operations to all data are made in accordance with file allocation table. Once file allocation table is damaged, operating system will be unable to locate data though this data is still stored completely in original place. Deleting a file is to write a deletion mark on the deleted file in file allocation table, which shows this file has been deleted and space released by this file can be used by other files. And real data are stored in data area safely. Therefore, as long as we remove the deletion mark by making use of special tools, deleted data can be recovered.
Formatting partition is similar to deleting files. It also operates file allocation table only, and the only difference is that formatting writes deletion mark to all files or empties the whole file allocation table while deleting just writes deletion mark to a certain or some files. By making use of data recovery tool, we are able to recover lost data.
From the introduction above, we see data recovery can be realized due to the special data storage principle. Nevertheless, data recovery should be on the condition that lost data are not overwritten by new data. Well then, what is data overwriting?
We have said space taken by the deleted or formatted file can be used by other files, including space both in file allocation table and data area. In other words, once users write new data to hard disk after mistaken deletion or formatting, the space released by lost data is very likely to be occupied by the new data. If this kind of situation emerges, users will be unable to recover lost data since this data has been overwritten by new data.
Now, users should know both deleted data and formatted data can be recovered by using data recovery tools.