DEFRAG.exe (Windows 10/ Server 2012/ 2012R2/ 2016)

Defragment hard drive volumes.

Syntax
      Perform analysis only:
      DEFRAGs /A  vol_to_defrag [Options]

      Defragment (default operation)
      DEFRAG [/D] vol_to_defrag [Options]

      Perform the proper optimization for each media type:
      DEFRAG /O vol_to_defrag [Options]

      Perform free space consolidation:
      DEFRAG /X vol_to_defrag [Options]

      Track an operation already in progress on a volume:
      DEFRAG /T volume

vol_to_defrag:

    This can be any of:

volume The drive letter or mount point path of the volume(s) to be defragmented or analyzed. To specify multiple volumes separate the names with spaces. /C Perform the operation on all volumes. /E volume_name(s) Perform the operation on all volumes Except those specified. Options: /G Optimize the storage tiers on the specified volumes. /H Run the operation at normal priority (default is low). /I n Run Tier optimization for at most n seconds on each volume. /K Perform slab consolidation on the specified volumes. /L Perform retrim on the specified volumes. /M [n] Run the operation on each volume in parallel in the background. At most n threads optimize the storage tiers in parallel. /U Print the progress of the operation on the screen. /V Print verbose output containing the fragmentation statistics.

Defrag has an undocumented option/b (boot optimisation) which will clear out the Windows\Prefetch directory. Deleting prefetch files will make the machine boot more slowly so this is not recommended.

A volume must have at least 15% free space for defrag to completely and adequately defragment it. defrag uses this space as a sorting area for file fragments.

Supported file systems: NTFS, ReFS, Fat or Fat32.

To run Defrag, you must be a member of the Administrators group on the local computer, or have been delegated the appropriate authority. When working defrag will display a blinking cursor.

On a tiered volume traditional defrag (/D) is performed only on the Capacity tier. (See FSUTIL tiering)

Some file system volumes or drives cannot be defragmented:

Volume names can be given either using the assigned drive letter (C:\) or the full volume name/path (\\?\Volume{...)

To obtain a list of volume_names using PowerShell:

PS C:\> Get-CimInstance Win32_Volume | Format-Table Name, Label, FreeSpace, Capacity

Free space consolidation (/X) takes all free sectors on the volume and arranges them together so they are contiguous. This is normally done only when you intend to re-size the volume with DISKPART SHRINK to make it smaller.
Ensure you have a good a backup before running any consolidate/shrink process as this has a tendency to fail.

Defrag's scheduled task runs as a maintenance task and by default is scheduled to run every 7 days at 2am. An Administrator can change the frequency using Optimize Drives application.

Examples

Analyse drive C: to see if it needs to be defragmented:

DEFRAG /A C:

Defragment drive c with verbose output saved to a file:

DEFRAG c: /U /V > FileName.txt

Defragment two drives in parallel:

DEFRAG C: D: /M

“This plastic doesn't go away by itself, and to just let hundreds of thousands of tons of plastic be out there to be fragmented into these small and dangerous microplastics to me seems like an unacceptable scenario” ~ Boyan Slat

Related commands

CleanMgr - Automated cleanup of Temp files, Internet files, downloaded files, recycle bin.
DISKPART - Partition manager.
Contig - Single-file defragmenter (SysInternals/Microsoft).
pagefileconfig.vbs - PageFile Configuration.


 
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