Windows – How to Copy Timestamps Only of Already Copied Files and Folders

Something like robocopy will be your best bet. USB drives can't handle a whole lot of IO to begin with.

I've pushed millions of small files to and from USB drives using robocopy. It takes time, but it gets the job done.

Here is a simple PowerShell script that will do what you are looking for. Change FolderA and FolderB appropriately. Also, the -whatif will just tell you what it will do without performing any actions. Once you verify it is what you are trying to do is correct, just remove the -whatif.

#This sets $FolderA to the directory you want to copy from    
$FolderA = "v:\FolderA"
#This sets $FolderB to the directory you want to copy to
$FolderB = "v:\FolderB" 
#This does the copy (Note the -whatif to make sure this is what you want)
Copy-Item -Path "$FolderA\*" -Destination $FolderB -WhatIf
#This does a compare of Directory A and B, and removes all files that only exist in Directory B that haven't been access for 7 days. (Again, notices the -whatif at the end)
Compare-Object (Get-ChildItem $FolderA) (Get-ChildItem $FolderB) ` #The [`] tells PowerShell the command will continue on the next line
    | where {$_.SideIndicator -eq "=>"} `
    | where {$_.InputObject.LastWriteTime -le (Get-Date).Adddays(-7)} `
    | Foreach { Remove-Item -Path $_.InputObject.FullName -WhatIf}