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Start-ReFSDedupJob

Starts a deduplication job on the specified ReFS volume.

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Last verified: 2026-10-26

Microsoft Microsoft.ReFsDedup.Commands reference: Starts a deduplication job on the specified ReFS volume. The syntax and selected example below are adapted from the pinned Windows Server 2025 reference. Module availability, target configuration and delegated permissions determine whether it can run in your environment. Documentation and parameter text: Microsoft, CC BY 4.0; formatting adapted by Cmdlet World. No execution testing is claimed.

Start-ReFSDedupJob [-Volume] <String> [-Duration <TimeSpan>] [-FullRun] [-CpuPercentage <UInt32>]
 [-ConcurrentOpenFiles <UInt32>] [-MinimumLastModifiedTimeHours <Int32>]
 [-ExcludeFileExtension <String[]>] [-ExcludeFolder <String[]>] [-CompressionFormat <Format>]
 [-CompressionLevel <UInt16>] [-CompressionChunkSize <UInt32>] [-CompressionTuning <UInt32>]
 [-RecompressionTuning <UInt32>] [-DecompressionTuning <UInt32>] [<CommonParameters>]

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Required permissions

Use an account with the target resource permissions documented for Start-ReFSDedupJob. Modifying administrative cmdlets may require elevation or delegated administration. This catalog does not assert that ordinary users can execute the command.

Supported environments

Windows / Microsoft.ReFsDedup.Commands · Windows Server 2025 documentation; feature/module prerequisites apply

Parameters

-CompressionChunkSize: Specifies the chunk size to use during compression.
-CompressionFormat: Specifies the compression format to use during the job. Acceptable values are: - LZ4 - Uncompressed - Unknown - ZSTD
-CompressionLevel: Specifies the compression level to use during the job.
-CompressionTuning: Specifies the compression tuning to use during the job.
-ConcurrentOpenFiles: Specifies the maximum number of files that can be open concurrently during the job.
-CpuPercentage: Specifies the maximum percentage of CPU to use during the job.
-DecompressionTuning: Specifies the decompression tuning to use during the job.
-Duration: Specifies the duration of the job.
-ExcludeFileExtension: Specifies one or more file extensions to exclude from the job.
-ExcludeFolder: Specifies one or more folders to exclude from the job.
-FullRun: Indicates whether to run a full deduplication job on the specified ReFS volume. If this parameter isn't specified, the job will run in incremental mode where only new or changed files will be processed.
-MinimumLastModifiedTimeHours: Specifies the minimum number of hours that must elapse before a file can be deduplicated.
-RecompressionTuning: Specifies the recompression tuning to use during deduplication.

Prerequisites

Windows with the Microsoft.ReFsDedup.Commands module and the Windows feature or management tools that provide it. Confirm target connectivity and version compatibility using the linked Microsoft reference.

Security considerations

This cmdlet changes system state. Review every target and parameter in the official reference, test outside production, and prepare an appropriate backup or rollback. Do not execute the example automatically.

Examples

Example 1

Start-ReFSDedupJob -Volume "D:"

This example starts a deduplication job on the D: drive using the default settings. Source: Microsoft, CC BY 4.0; transcript prompt/output removed. This example was not executed.

Sources

https://github.com/MicrosoftDocs/windows-powershell-docs/blob/b7645dd8c687139b28e845119da30ec670526507/docset/winserver2025-ps/Microsoft.ReFsDedup.Commands/Start-ReFSDedupJob.md

https://learn.microsoft.com/powershell/module/microsoft.refsdedup.commands/start-refsdedupjob?view=windowsserver2025-ps

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