Why is my MFT his big, how to reduce the size?


can anyone tell me how do i get the size of the mft down on my external hdd?? :doh:

I have O&O set to defrag using ‘access’ method which supposedly needs a bigger hdd space, so ive now started defragging using ‘name’ method but am not sure if this will get the mft down.

After doing some googling, I think the answer is not very easily! Possibly by reformatting the HD. :frowning: But if your HDD gets full, XP will automatically use the space reserved for the MFT to store files. Try starting here .

Diskeeper will change MFT size, and also defrag the MFT on reboot. It also will check all MFT file sizes and recommend what to do with it.

The MFT is the heart of an NTFS partition. There is at least one entry in the MFT for every file on an NTFS volume. All the information about a file, including its’ size, time and date stamps, permissions, data content, etc. are stored in the MFT (or in space described by the MFT).

To prevent fragmentation of the MFT, NTFS reserves space for the MFT in an effort to keep it as contiguous as it grows. This is important because defraggers can not move MFT records and fragmentation of the MFT can severely impact performance.

When you add files to an NTFS volume, entries are added to the MFT. When files are deleted from an NTFS volume, their MFT entries are marked as free and may be reused, but the MFT does not shrink. Thus, space used by these entries is not reclaimed from the disk.

NTFS reserves a percentage of the volume for exclusive use of the MFT. Space for files and directories will not be allocated from this MFT zone until all other space is allocated first. Depending on the average file size and other variables, either the reserved MFT zone or the unreserved space on the disk may be filled first. Volumes with a few large files will exhaust the unreserved space first, while volumes with a large number of small files will exhaust the MFT zone space first. When either the MFT zone or the unreserved space fills, fragmentation of the MFT starts. If the unreserved space becomes full, space for user files and directories will be allocated from the MFT zone. If the MFT zone becomes full, space for new MFT entries will be allocated from the remainder of the disk.

You can impact the amount of space NTFS reserves for the MFT by editing:


Add Value name NtfsMftZoneReservation as a type REG_DWORD and set the data value. The valid range is 1 - 4.

Value: 1 12.5% of free space, default
Value: 2 25% of free space
Value: 3 37.5% of free space
Value: 4 50% of free space

NOTE: This is a run-time parameter and does not affect the format of a volume. It affects the way NTFS allocates space on all volumes. To be completely effective, this entry should in effect at the time you format a volume.

:cool: :cool:

hmm, cheers for the info. From what youve said can i understand that if the disk is full , mft will be reduces to accomodate more files or not?? :frowning:

Not true, a number of defraggers can defrag the MFT, see my post above.

Yes I know that perfectdisk can defrag MFT, But that is not what he is asking. He is asking why the MFT zone is so big. The MFT can only be defrag in the boot process. For the average user the is no need to be messing around with the MFT zone.

:cool: :cool:

@ gregtherotterius

Your MFT zone is as small as your going to be able is make it. Don’t look at the zone as space being wasted, Window OS applications can still write and store in the zone. Look at the zone as being a safety net.

:cool: :cool:

Sorry Diskeeper

Anyways there is no need to be playing with the MFT zone.

:cool: :cool:

Just an FYI, there is a freeware program out there called Eraser. It gets rid of the MFTzone. Since PerfectDisk (which I use) defrags the MFT, I have now no need to have a 125g block reserved on my disk…

turn system restore off on these external hard drive.

turn system restore on if u need.

or u can always format the Hard Drive.

[B]RayLNelson[/B] -

Just an FYI, there is a freeware program out there called Eraser.


It gets rid of the MFTzone.

Not true. [B]There is NOT any option that[/B] during the erasing of the free space [B]do that[/B]. The program (v5.8.8 standalone) have some cleaning options, yet “Overwrite - Free Disk Space (and Master File Table Records)” did not mean that the MFT shrink, nor that the reserved size for it do change in any way, shape or form. (not to mention capacity)

And that is the whole issue. [B]We simply are seeking to control the reserved MFT space size[/B].

Since PerfectDisk (which I use) defrags the MFT, I have now no need to have a 125g block reserved on my disk…

Maybe it did not show to you, but I seriously dubt that PerfectDisk do something with MFT at all. Also I can’t trust your claim after the fiasco with Eraser… before erasing I had 9312MB free, after erasing I have 9299Mb free… so thx to you&Eraser I lost another 13MB :a

IMHO tweaking with MFT will require that the drive is not initialized in windows at minimum.

PS. to make my post more usefull, then the MFT size can be tweaked within the 12.5 - 50% of free space on drive also by this:
fsutil behavior set mftzone 1
fsutil behavior set mftzone 4

Sadly there is no way to get it bellow these 12.5% - or at least I did not find any way to do. Almost definitively it can’t be even done at live NTFS drive…

I’ve used & been satisfied with Eraser for a long time.
However it only overwrites unused space even in the MFT.
I’m not sure why it added the 13MB . I guess it may move found data fragmented in unused space but not detected by the OS . I’m not certain of that.
This may be the explanation from Erasers’ help:
"Eraser creates maximum length files until the unused entries in the Master File Table are overwritten. "
I use v 5.86.1

Well, their homepage does not work right now ( http://eraser.heidi.ie ), so I can’t show you, that far more others are complained about the very same thing - after “cleaning free space” are the free space on HDD smaller a bit.

That a “bit” contradict the idea to use Eraser. I care about not only wiping out the already not used files in MFT (CCleaner can do it, for christ sake!), but more about the resize of it. To allow more free space for defragmentation…

And that is what I wanted to do. I jumped the Eraser because of the false claim presented above, and that it is. I did not store anything that I need to kill traces off on my HDD (and if I do it, I will use FAT32 and never ever NTFS) and therefore Eraser is not for me. I only care, if there is any app, that can shring the reserved MFt space on HDD. Likely it has to be on boot CD (like Hiren boot CD), because as long, as the NTFS volume are “live”, then the MFT are somewhat locked by the filesystem itself…

I’m not an expert on Eraser just a long time user.
I remember in the Windows98 SE I used the eraserd.exe that would run before Windows 98 started in a DOS environment. Of course that was FAT32.
I think I tried to get this to work with NTFS & it didn’t . That was quite a while ago.
I may see if it is still possible. Even if it will I don’t remember a setting for the MFT & eraserd.exe
I found nothing in the Eraser help that said it would shrink reserved MFT space on HDD. Member RayLNelson posted it did but I beleive this is incorrect .
If there is unused space in the MFT it should overwrite it . Eraser has no settings I can find to shrink used space in the MFT.