Optimize-Volume -DriveLetter mydriveletter -ReTrim
so, something like this
Optimize-Volume -DriveLetter E -ReTrim -VerboseVERBOSE: Invoking retrim on Shared_Transfer (E:)...
VERBOSE: Performing pass 1:
VERBOSE: Retrim: 0% complete...
VERBOSE: Retrim: 100% complete.
VERBOSE:
Post Defragmentation Report:
VERBOSE:
Volume Information:
VERBOSE: Volume size = 99.99 GB
VERBOSE: Cluster size = 4 KB
VERBOSE: Used space = 82.22 GB
VERBOSE: Free space = 17.77 GB
VERBOSE:
Retrim:
VERBOSE: Backed allocations = 100
VERBOSE: Allocations trimmed = 36
VERBOSE: Total space trimmed = 16.79 GB