I encountered a number of clusters that had /scratch location configured incorrectly, many due to LUN migrations to new storage frames, and some that were never changed from default. For consistent configuration, due to the number of hosts & clusters involved, a script was needed.

I found the following via Google, which appears to be created by fellow vExpert “Virtual Nomad” Askar Kopbayev:
Automating configuration of a scratch location for ESXi with PowerCLI

I had to tweak just a few things to work for my environment:

# original source by vmnomad - https://community.spiceworks.com/scripts/show/3686-automating-configuration-of-a-scratch-location-for-esxi-with-powercli
# modified by @vMiklm - miklm.com - 19 January 2018
# Example use:
# PS> .\set-scratch.ps1 $vCenter $Cluster $Datastore $Folder
# PS> .\set-scratch.ps1 vcenter.local clusteresx08 SharedNFS01 scratch/clusteresx08

#Collect the vCenter, Cluster, Scratch_datastore & Folder
Param([String]$vCenter, [String]$Cluster, [String]$Datastore, [String]$Folder)

#Function to use multiple colors in one command
function Write-Color([String[]]$Text, [ConsoleColor[]]$Color) {
    for ($i = 0; $i -lt $Text.Length; $i++) {
        Write-Host $Text[$i] -Foreground $Color[$i] -NoNewLine
    }
    Write-Host
}

#defining array variables
$vmhost_array =@()
$dir = @()
$reboot_servers = @()

#Validating input
if (!$vCenter){
  Write-Color  -Text "Please provide valid vCenter name using ","'-vCenter' ","option, exiting.." -Color Gray,Red,Gray
  exit
}

if (!$Cluster){
  Write-Color  -Text "Please provide valid cluster name using ","'-Cluster' ","option, exiting.." -Color Gray,Red,Gray
  exit
}

if (!$Datastore){
  Write-Color  -Text "Please provide valid Datastore name using ","'-Datastore' ","option, exiting.." -Color Gray,Red,Gray
  exit
}

if (!$Folder){
  Write-Color  -Text "Please provide valid scratch folder name using ","'-Folder' ","option, exiting.." -Color Gray,Red,Gray
  exit
}

#Getting the path of the script
$scriptPath = split-path -parent $MyInvocation.MyCommand.Definition

#Connecting to vCenter server
Write-Color -Text "`nConnecting to ", $vCenter -Color Gray, Red
Connect-VIserver $vCenter | Out-Null

#Validating connection to vCenter
if(!$DefaultVIServers){
  Write-Color -Text "`nConnection to ",$vCenter," failed, exiting.." -Color Yellow,Red,Yellow
  exit
} elseif($DefaultVIServer.name -ne $vCenter){
    Write-Color -Text "Connected to wrong vCenter ", $DefaultVIServer.name ", exiting.." -Color Yellow,Red,Yellow
  } else {
  Write-Color -Text "Connection to vCenter ", $vCenter, " succeeded" -Color Green,Red,Green
  Write-Host
}

#Getting the list of the ESXi hosts in the $Cluster
$vmhost_array = get-cluster -name $cluster | Get-VMhost

#Mounting datastore to be used as a scratch location
New-PSDrive -Name "DS" -Root \ -PSProvider VimDatastore -Datastore (Get-VMHost -Name $vmhost_array[0] | Get-Datastore $datastore) | out-null
Set-Location DS:\$folder

#Collect the list of the folders
$dir = dir

#Check if the scratch folders exist for the ESXi hosts and create missing folders
Foreach ($vmhost in $vmhost_array)
{
If ($dir.name -contains $vmhost.name){
  Continue
  }
else{
  Write-Color -Text "`n Creating scratch folder for ", $vmhost -Color Green,Red
  mkdir $vmhost | out-null
  }
}

#Getting Scratch datastore [was getting UUID, didn't work, vCenter will convert it anyway -MM]
$dstorep = Get-VMhost $vmhost | Get-Datastore $Datastore

#Check if the ESXi host is already configured with correct scratch location
Foreach ($vmhost in $vmhost_array){
  $row = '' | Select Server_Name
  $configured_scratch = (Get-VMhost $vmhost | Get-AdvancedSetting -Name "ScratchConfig.ConfiguredScratchLocation").value
  $current_scratch = (Get-VMhost $vmhost | Get-AdvancedSetting -Name "ScratchConfig.CurrentScratchLocation").value
  $correct_scratch = "/vmfs/volumes/"+$dstorep+"/"+$folder+"/"+$vmhost
# Write-Host "`n Correct scratch is" $correct_scratch
# Write-Host "`n Configured Scratch on" $vmhost "is" $configured_scratch
# Write-Host "`n Current Scratch on" $vmhost "is" $current_scratch
  If (($configured_scratch -eq $correct_scratch) -and ($current_scratch -eq $correct_scratch)) {
    Write-Color -Text "`n ESXi host ", $vmhost, " was already configured with the correct scratch location" -Color Green,Red,Green
  } elseif($configured_scratch -eq $correct_scratch) {
  Write-Color -Text "`n The ESXi host", $vmhost, " was already configured correctly, `n but it hasn't been restared after the configuration change" -Color Yellow,Red,Yellow
  $row.Server_Name = $vmhost.Name
  $reboot_servers += $row
  } else {
    Get-VMhost $vmhost | Get-AdvancedSetting -Name "ScratchConfig.ConfiguredScratchLocation" | Set-AdvancedSetting -Value "$correct_scratch" -Confirm:$false | out-null
    Write-Host -Fore:Red "`n ESXi host" $vmhost "is configured with the correct scratch location"
    $row.Server_Name = $vmhost.Name
    $reboot_servers += $row
  }
}

#Provide output with the list of ESXi servers to be rebooted for the configration change to take effect
Write-Host -Fore:Green "`n The configuration of the scratch location for ESXi servers in cluster" $cluster "is complete"
Write-Host -Fore:Green "`n The following ESXi hosts have to be rebooted for the configuration change to take effect:"
foreach ( $server in $reboot_servers ) {
Write-Host -Fore:Red `n $server.Server_Name
}

#Exporting the list of ESXi hosts to be rebooted
$exportfilename =  "Servers_to_reboot.csv"
$exportfilepath = Join-Path -Path $scriptPath -ChildPath $exportFileName
$reboot_servers | Export-Csv -Path $exportFilePath -NoTypeInformation -Force
Write-Host "`n This list of these servers has also been exported to" $exportfilepath

#Change location back to original
Set-Location $scriptPath