What Is an MFT Entry?

A Windows hard drive using the native NTFS file system has a database called the master file table in which the names and locations of the files on the drive are stored. Each file on your computer is referenced by at least one MFT entry. The size and status of the master file table affects your computer's reliability and performance.

Fragmentation

When you format a hard drive using the NTFS file system, Windows allocates a portion of the drive for the master file table. As you add files to the drive, the MFT grows; it does not shrink, however, when you delete files. As a result, the MFT may eventually outgrow the space allocated to it and begin using space normally reserved for your files. When this happens, the MFT may become fragmented, and the amount of time it takes Windows to find files on the hard drive increases. You can use a disk defragmentation utility to resolve this issue.

Performance

Once the MFT has exceeded its allocated space on your computer's hard drive and entered the general data storage area, fragmentation becomes a recurring issue. The Windows registry entry that determines the size of the reserved space is named "NtfsMFTZoneReservation." You can change this value to increase the reserved space and prevent fragmentation from occurring. Unfortunately, the change does not take effect until you reformat the hard drive.

File Recovery

When you delete a file, Windows removes its entry from the master file table and marks the space as available for other files. The deleted file remains on the hard drive until Windows overwrites it with other data. You can use this to your advantage if you delete a file accidentally. File recovery programs can scan the hard drive for files not referenced on the MFT and restore them for you. Many of these software applications are free.

Corruption

The NTFS file system backs up the master file table automatically and copies the backup over the original MFT if it detects damage to the file structure. In this way, NTFS is resilient to MFT corruption. In rare instances, however, both the MFT and its backup can fail. In this situation, Windows may be able to recover some portion of the lost data. You can check a hard drive for errors from the "Computer" screen by right-clicking the hard drive and selecting "Properties." Click the "Check Now" button under the "Tools" tab to run the error-checking utility.