SpotFix: Takes the volume briefly offline and then fixes only issues that are logged in the $corrupt file (equivalent to chkdsk /spotfix).
If Repair-Volume, or even chkdsk.exe, discovers an error, it will be recorded in a hidden system file $corrupt. This is not a PowerShell variable. Initiate fixing the errors using the Powershell cmdlet –SpotFix, which skips running any sort of scan.
PS C:\> repair-volume -DriveLetter D –spotfix -asjob
More information can be found here: http://technet.microsoft.com/en-us/library/hh848662.aspx