==============================
"NTFS journaling" refers to the NTFS change journal which provides a persistent log of changes made to files on a volume. NTFS maintains the change journal by tracking information about added, deleted, and modified files for each volume.
An automatic backup application is one example of a program that must check for changes to the state of a volume to perform its task. The brute force method of checking for changes in directories or files is to scan the entire volume. However, this is often not an acceptable approach because of the decrease in system performance it would cause.
Also, if a large number of directories and files must be backed up, the amount of processing and memory overhead for such an application might also cause the operating system's performance to decrease.
To avoid these disadvantages, the NTFS file system maintains a change journal. When any change is made to a file or directory in a volume, the change journal for that volume is updated with a description of the change and the name of the file or directory.
Change journals are also needed to recover file system indexing - for example after a computer or volume failure. The ability to recover indexing means the file system can avoid the time-consuming process of reindexing the entire volume in such cases.
==============================