NTFS overview

Applies to: Windows Server 2022, Windows 10, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, Windows Server 2008

NTFS, the primary file system for recent versions of Windows and Windows Server, provides a full set of features including security descriptors, encryption, disk quotas, and rich metadata. It can be used with Cluster Shared Volumes (CSV) to provide continuously available volumes that can be accessed simultaneously from multiple nodes of a failover cluster.

For more feature information, see the Related links section of this article. To learn about the newer Resilient File System (ReFS), see Resilient File System (ReFS) overview.

Increased reliability

NTFS uses its log file and checkpoint information to restore the consistency of the file system when the computer is restarted after a system failure. After a bad-sector error, NTFS dynamically remaps the cluster that contains the bad sector, and allocates a new cluster for the data. It also marks the original cluster as bad, and no longer uses the old cluster. For example, after a server crash, NTFS can recover data by replaying its log files.

NTFS continuously monitors and corrects transient corruption issues in the background without taking the volume offline. This feature is known as self-healing NTFS, which was introduced in Windows Server 2008.

For larger corruption issues, the Chkdsk utility, in Windows Server 2012 and later, scans and analyzes the drive while the volume is online, limiting time offline to the time required to restore data consistency on the volume. When you use NTFS with Cluster Shared Volumes, no downtime is required. For more information, see NTFS Health and Chkdsk.

Increased security

  • Access Control List (ACL)-based security for files and folders: NTFS lets you set permissions on a file or folder, specify the groups and users whose access you want to restrict or allow, and select access type.

  • Support for BitLocker Drive Encryption: BitLocker Drive Encryption provides more security for critical system information and other data stored on NTFS volumes. Beginning in Windows Server 2012 R2 and Windows 8.1, BitLocker provides support for device encryption on x86 and x64-based computers with a Trusted Platform Module (TPM) that supports connected stand-by (previously available only on Windows RT devices). Device encryption helps protect data on Windows-based computers, and it helps block malicious users from accessing the system files they rely on to discover the user's password. It also prevents malicious users from accessing a drive by physically removing it from the PC and installing it on a different one. For more information, see What's new in BitLocker.

Support for large volumes

NTFS can support volumes as large as 8 petabytes on Windows Server 2019 and newer and Windows 10, version 1709 and newer (older versions support up to 256 TB). Supported volume sizes are affected by the cluster size and the number of clusters. With (232 – 1) clusters (the maximum number of clusters that NTFS supports), the following volume and file sizes are supported.

Cluster size Largest volume and file
4 KB (default size) 16 TB
8 KB 32 TB
16 KB 64 TB
32 KB 128 TB
64 KB (earlier max) 256 TB
128 KB 512 TB
256 KB 1 PB
512 KB 2 PB
1024 KB 4 PB
2048 KB (max size) 8 PB

If you try to mount a volume with a cluster size larger than the supported maximum of the Windows version you're using, you get the error STATUS_UNRECOGNIZED_VOLUME.


Services and apps might impose additional limits on file and volume sizes. For example, the volume size limit is 64 TB if you're using the Previous Versions feature or a backup app that makes use of Volume Shadow Copy Service (VSS) snapshots (and you're not using a SAN or RAID enclosure). However, you might need to use smaller volume sizes depending on your workload and the performance of your storage.

Formatting requirements for large files

To allow proper extension of large VDHX files, there are new recommendations for formatting volumes. When formatting volumes that you use with Data Deduplication or that host very large files, such as VDHX files larger than 1 TB, use the Format-Volume cmdlet in Windows PowerShell with the following parameters.

Parameter Description
-AllocationUnitSize 64KB Sets a 64-KB NTFS allocation unit size.
-UseLargeFRS Enables support for large file record segments (FRS). Using this parameter increases the number of extents allowed per file on the volume. For large FRS records, the limit increases from about 1.5 million extents to about 6 million extents.

For example, the following cmdlet formats drive D as an NTFS volume, with FRS enabled and an allocation unit size of 64 KB.

Format-Volume -DriveLetter D -FileSystem NTFS -AllocationUnitSize 64KB -UseLargeFRS

You also can use the format command. At a system command prompt, enter the following command, where /L formats a large FRS volume and /A:64k sets a 64-KB allocation unit size:

format /L /A:64k

Maximum file name and path

NTFS supports long file names and extended-length paths, with the following maximum values:

  • Support for long file names, with backward compatibility: NTFS supports long file names, storing an 8.3 alias on disk (in Unicode) to provide compatibility with file systems that impose an 8.3 limit on file names and extensions. If needed (for performance reasons), you can selectively disable 8.3 aliasing on individual NTFS volumes in Windows Server 2008 R2, Windows 8, and more recent versions of the Windows operating system. In Windows Server 2008 R2 and later systems, short names are disabled by default when a volume is formatted using the operating system. For application compatibility, short names still are enabled on the system volume.

  • Support for extended-length paths: Many Windows API functions have Unicode versions that allow an extended-length path of approximately 32,767 characters. That total is well beyond the 260-character path limit defined by the MAX_PATH setting. For detailed file name and path format requirements, and guidance for implementing extended-length paths, see Naming files, paths, and namespaces.

  • Clustered storage: When used in failover clusters, NTFS supports continuously available volumes that can be accessed by multiple cluster nodes simultaneously when used with the Cluster Shared Volumes (CSV) file system. For more information, see Use Cluster Shared Volumes in a failover cluster.

Flexible allocation of capacity

If the space on a volume is limited, NTFS provides the following ways to work with the storage capacity of a server:

  • Use disk quotas to track and control disk space usage on NTFS volumes for individual users.
  • Use file system compression to maximize the amount of data that can be stored.
  • Increase the size of an NTFS volume by adding unallocated space from the same disk or from a different disk.
  • Mount a volume at any empty folder on a local NTFS volume if you run out of drive letters or need to create extra space that is accessible from an existing folder.