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How to change the MFT zone size: Question for jrhelgeson

Posted on 1998-02-24
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Last Modified: 2013-12-28
How can I make the MFT zone larger if I expect to have a large number of small files on an NTFS partition?
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Question by:y96andha
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jrhelgeson earned 250 total points
ID: 1790891
FYI on MFT
==========
The NTFS file system contains, at its heart, a file called the master file table or "MFT". There is at least one entry in the MFT for every file on an NTFS volume, including the MFT itself.

Because utilities that defragment NTFS volumes cannot move MFT entries, and because excessive fragmentation of the MFT can
impact performance, NTFS reserves space for the MFT in an effort to keep the MFT as contiguous as possibleas it grows.

MORE INFORMATION
================
NTFS uses MFT entries to define the files they correspond to. All information about a file, including its size, time and date stamps, permissions, data content, etc is either stored within MFT entries or in space external to the MFT but described by the MFT entries. (Directory entries, external to the MFT, also contain some redundant information regarding files.)

As files are added to an NTFS volume, more entries are added to the MFT and so the MFT grows. 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.

Because of the importance of the MFT to NTFS and the possible impact on performance if this file becomes highly fragmented,
NTFS makes a special effort to keep this file contiguous. NTFS reserves a percentage of the volume for exclusive use of the MFT
until and unless the remainder of the volume is completely used up. Thus, 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 used up before the other as the disk fills to capacity.

Volumes with a small number of relatively large files will exhaust the unreserved space first, while volumes with a large number of relatively small files will exhaust the MFT zone space first. In either case, fragmentation of the MFT starts to take place when one region or the other becomes full. If the unreserved space becomes full, space for user files and directories will start to be allocated from the MFT zone competing with the MFT for allocation. If the MFT zone becomes full, space for new MFT entries will be allocated from the remainder of the disk, again competing with other files.

YOUR ANSWER!
============
Beginning in service pack 4 for Windows NT version 4, to better accommodate volumes that must hold a large number of small files, a new registry parameter is being introduced that can increase the percentage of a volume that NTFS will reserve for its master file table. NtfsMftZoneReservation is a REG_DWORD that can take on a value between 1 and 4, where 1 corresponds to the minimum   MFT zone size and 4 corresponds to the maximum. If the arameter is not specified or an invalid value is supplied, NTFS will use a
default value of 1 for this parameter. The exact ratios that correspond to each setting are undocumented because they are not set in stone and may change in future releases. In order to know what setting is best for your environment, it may be necessary to
experiment with different values.

1. Run Registry Editor (Regedt32.exe).

2. Under the HKEY_LOCAL_MACHINE, go to the following subkey:
                                    System\CurrentControlSet\Control\FileSystem

3. Click the Edit menu and click Add Value.

4. Add the following information in the dialog box:
Value Name: NtfsMftZoneReservation
Data Type : REG_DWORD
Data : (valid range is 1-4)
Note: This is a run-time parameter and does not affect the format of a volume. Rather, it affects the way NTFS allocates space on all volumes on a given system. Therefore, in order to be completely effective, the parameter must be in effect from the time that a volume is formatted throughout the life of the volume. FYI on MFT
==========
The NTFS file system contains, at its heart, a file called the master file table or "MFT". There is at least one entry in the MFT for every file on an NTFS volume, including the MFT itself.

Because utilities that defragment NTFS volumes cannot move MFT entries, and because excessive fragmentation of the MFT can      impact performance, NTFS reserves space for the MFT in an effort to keep the MFT as contiguous as possibleas it grows.

MORE INFORMATION
================
NTFS uses MFT entries to define the files they correspond to. All information about a file, including its size, time and date stamps, permissions, data content, etc is either stored within MFT entries or in space external to the MFT but described by the MFT entries. (Directory entries, external to the MFT, also contain some redundant information regarding files.)

As files are added to an NTFS volume, more entries are added to the MFT and so the MFT grows. 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.

Because of the importance of the MFT to NTFS and the possible impact on performance if this file becomes highly fragmented,
NTFS makes a special effort to keep this file contiguous. NTFS reserves a percentage of the volume for exclusive use of the MFT
until and unless the remainder of the volume is completely used up. Thus, 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
used up before the other as the disk fills to capacity.

Volumes with a small number of relatively large files will exhaust the unreserved space first, while volumes with a large number of relatively small files will exhaust the MFT zone space first. In either case, fragmentation of the MFT starts to take place when one region or the other becomes full. If the unreserved space becomes full, space for user files and directories will start to be allocated from the MFT zone competing with the MFT for allocation. If the MFT zone becomes full, space for new MFT entries will be allocated from the remainder of the disk, again competing with other files.

YOUR ANSWER!
============
Beginning in service pack 4 for Windows NT version 4, to better accommodate volumes that must hold a large number of small files,
a new registry parameter is being introduced that can increase the percentage of a volume that NTFS will reserve for its master file table. NtfsMftZoneReservation is a REG_DWORD that can take on a value between 1 and 4, where 1 corresponds to the minimum
MFT zone size and 4 corresponds to the maximum. If the arameter is not specified or an invalid value is supplied, NTFS will use a
default value of 1 for this parameter. The exact ratios that correspond to each setting are undocumented because they are not set in stone and may change in future releases. In order to know what setting is best for your environment, it may be necessary to

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