Understanding ReFSUtil

The Resilient File System (ReFS) is designed to maximize data availability, scale efficiently to large data sets, and ensure data integrity. Despite its robustness, ReFS volumes can become corrupted due to unforeseen events like power failures, leading to inaccessible data. In such scenarios, Microsoft‘s ReFSUtil command-line tool becomes invaluable for diagnosing and recovering data from damaged ReFS volumes.

Understanding ReFSUtil

ReFSUtil is a utility included in Windows and Windows Server, located in the %SystemRoot%\System32 directory. Its primary function is to diagnose severely damaged ReFS volumes, identify recoverable files, and copy them to another location. This tool is particularly useful when a volume appears as RAW in Disk Management, indicating significant corruption.

Key Features and Parameters

ReFSUtil offers several parameters to facilitate data recovery:

• <source volume>: Specifies the ReFS volume to process, formatted as “L:” or as a path to the volume mount point.
• <working directory>: Designates a location to store temporary information and logs, which must not reside on the <source volume>.
• <target directory>: Indicates where identified files will be copied; this also must not be on the <source volume>.
• -m: Recovers all possible files, including deleted ones. Note: This can extend processing time and may yield unexpected results.
• -v: Enables verbose mode for detailed output.
• -x: Forces the volume to dismount first if necessary, invalidating all open handles to the volume.

Operating Modes

ReFSUtil operates in various modes to accommodate different recovery needs:

Quick Automatic Mode

Performs a Quick Scan followed by a Copy Phase. This mode assumes some critical structures are intact, reducing scan time and minimizing the recovery of stale files.

Usage:

refsutil salvage -QA <source volume> <working directory> <target directory> <options>

Full Automatic Mode

Conducts a comprehensive scan of the entire volume, which may be time-consuming but is thorough in locating recoverable files.

Usage:

refsutil salvage -FA <source volume> <working directory> <target directory> <options>

Diagnose Phase (Manual Mode)

Assesses whether the specified volume is an ReFS volume and determines its mountability, providing reasons if it’s not mountable.

Usage:

refsutil salvage -D <source volume> <working directory> <options>

Quick Scan Phase

Performs a swift scan for recoverable files, assuming some volume structures aren’t corrupted. Discovered files are logged in the foundfiles.<volume signature>.txt within the working directory.

Usage:

refsutil salvage -QS <source volume> <working directory> <options>

Full Scan Phase

Scans the entire volume for recoverable files, which may take longer but is more exhaustive. Results are logged similarly to the Quick Scan.

Usage:

refsutil salvage -FS <source volume> <working directory> <options>

Copy Phase

Copies files listed in the foundfiles.<volume signature>.txt to the target directory.

Usage:

refsutil salvage -C <source volume> <working directory> <target directory> <options>

Copy Phase with List

Copies files specified in a user-defined list from the source volume to the target directory. This list is derived from the foundfiles.<volume signature>.txt file.

Usage:

refsutil salvage -SL <source volume> <working directory> <target directory> <file list> <options>

Copy Phase with Interactive Console

For advanced users, this mode allows file salvaging through an interactive console, requiring prior Scan Phase files.

Usage:

refsutil salvage -IC <source volume> <working directory> <options>

Practical Application

Consider a scenario where drive E: is a corrupted ReFS volume. To recover data using Quick Automatic mode, create working and target directories on a different drive, say C:\Temp and C:\Recover. Then, execute:

refsutil salvage -QA E: C:\Temp C:\Recover

This command initiates a quick scan of the E: drive, logging progress in C:\Temp and recovering files to C:\Recover.

Version Compatibility Considerations

It’s crucial to ensure that the version of ReFSUtil matches the ReFS version of your volume. Users have reported issues when attempting to use ReFSUtil on volumes with unsupported ReFS versions. For instance, ReFSUtil included with Windows Server 2022 doesn’t support volumes with ReFS version 3.7, leading to errors. In such cases, using a compatible version of ReFSUtil, such as the one from Windows 11, can resolve the issue.

Conclusion

ReFSUtil is an essential tool for maintaining Windows ReFS volumes. Whether you need to verify integrity, repair corruption, or optimize performance, mastering this command-line utility enhances your ability to manage resilient storage environments. By incorporating ReFSUtil into routine maintenance, IT professionals can ensure reliability and efficiency in their storage systems.