If a file contains information, it always occupies at least one allocation block.

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Locate and correct disk space problems on NTFS volumes

• Article
• 09/24/2021
• 11 minutes to read

In this article

This article discusses how to check an NTFS file system's disk space allocation to discover offending files and folders or look for volume corruption in Microsoft Windows Server 2003-based computers.

Applies to:   Windows Server 2003
Original KB number:   814594

Summary

NTFS supports many volume and file-level features that may lead to what appear to be lost or incorrectly reported free disk space. For example, an NTFS volume may suddenly appear to become full for no reason, and an administrator cannot find the cause or locate the offending folders and files. This may occur if malicious or unauthorized access to an NTFS volume where large files or a high quantity of small files are secretly copied has occurred. These files then have their NTFS permissions removed or restricted. This behavior may also occur after a computer malfunction or power outage occurs that cause volume corruption.

The disk space allocation of an NTFS volume may appear to be misreported for any of the following reasons:

• The NTFS volume's cluster size is too large for the average-sized files that are stored there.
• File attributes or NTFS permissions prevent Windows Explorer or a Windows command prompt from displaying or accessing files or folders.
• The folder path exceeds 255 characters.
• Folders or files contain invalid or reserved file names.
• NTFS metafiles [such as the Master File Table] have grown, and you cannot de-allocate them.
• Files or folders contain alternate data streams.
• NTFS corruption causes free space to be reported as in use.
• Other NTFS features may cause file-allocation confusion.

The following information can help you to optimize, repair, or gain a better understanding of how your NTFS volumes use disk space.

Cluster size is too large

Only files and folders that include internal NTFS metafiles like the Master File Table [MFT], folder indexes, and others can consume disk space. These files and folders consume all the file space allocations by using multiples of a cluster. A cluster is a collection of contiguous sectors. The cluster size is determined by the partition size when the volume is formatted.

For more information about clusters, see Default cluster size for NTFS, FAT, and exFAT.

When a file is created, it consumes a minimum of a single cluster of disk space, depending on the initial file size. When data is later added to a file, NTFS increases the file's allocation in multiples of the cluster size.

To determine the current cluster size and volume statistics, run a read-only chkdsk command from a command prompt. To do so, follow these steps:

1. Click Start, click Run, type cmd, and then click OK.

2. At the command prompt, type the command: chkdsk d:.

   Where d: is the letter of the drive that you want to check.

3. Click OK.

4. View the resulting output. For example:

   4096543 KB total disk space.