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NTFSInfo v1.0

By Mark Russinovich

Published: November 1, 2006

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Introduction

NTFSInfo is a little applet that shows you information about NTFS volumes. Its dump includes the size of a drive's allocation units, where key NTFS files are located, and the sizes of the NTFS metadata files on the volume. This information is typically of little more than curiosity value, but NTFSInfo does show some interesting things. For example, you've probably heard about the NTFS equivalent of the FAT file system's File Allocation Table. Its called the Master File Table (MFT), and it is made up of constant sized records that describe the location of all the files and directories on the drive. What's surprising about the MFT is that it is managed as a file, just like any other. NTFSInfo will show you where on the disk (in terms of clusters) the MFT is located and how large it is, in addition to specifying how large the volume's clusters and MFT records are. In order to protect the MFT from fragmentation, NTFS reserves a portion of the disk around the MFT that it will not allocate to other files unless disk space runs low. This area is known as the MFT-Zone and NTFSInfo will tell you where on the disk the MFT-Zone is located and what percentage of the drive is reserved for it.

You might also be surprised to know that like the MFT, all NTFS meta-data are managed in files. For instance, there is a file called $Boot that is mapped to cover the drive's boot sector. The volume's cluster map is maintained in another file named $Bitmap. These files reside right in the NTFS root directory, but you can't see them unless you know they are there. Try typing "dir /ah $boot" at the root directory of an NTFS volume and you'll actually see the $boot file. NTFSInfo performs the equivalent of the "dir /ah" to show you the names and sizes of all of NTFS (3.51 and 4.0) meta-data files.

NTFSInfo is intended to accompany my January 1998 Windows NT Magazine "NT Internals" column, which describes NTFS internal data structures.

Installation and Usage

NTFSInfo works on all versions of NTFS, but NTFS for Windows NT 5.0 has different meta-data files that NTFSInfo has not been programmed for yet. In order for NTFSInfo to work you must have administrative privilege.

Usage: NTFSInfo x

xThe drive letter of the NTFS volume that you want to examine.

How It Works

NTFSInfo uses an undocumented File System Control (FSCTL) call to obtain information from NTFS about a volume. It prints this information along with a directory dump of NTFS meta-data files.

 

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Runs on:

  • Client: Windows XP and higher.
  • Server: Windows Server 2003 and higher.