IOPs & Latency For Each VM

This is my first time writing a script to pull metrics from the virtual environment and I am trying to pull out the total disk latency and disk iops for each VM in the environment.

Here are the relevant portions that I have so far:

#Get powered on VMs

$VMs = Get-VM | ?{$_.powerstate -eq "PoweredOn"}

 

#Loop through each VM

foreach ($vm in $VMs) {

     $dskreadlatency = Get-Stat -Entity $vm -Stat "disk.totalreadlatency.average" -Start $start -Finish $end

     $dskwritelatency = Get-Stat -Entity $vm -Stat "disk.totalwritelatency.average" -Start $start -Finish $end

     $dsknumberwrites = Get-Stat -Entity $vm -Stat "virtualdisk.numberwriteaveraged.average" -Start $start -Finish $end

     $dsknumberreads= Get-Stat -Entity $vm -Stat "virtualdisk.numberreadaveraged.average" -Start $start -Finish $end         

}

 

#setting fields to the averages of the stats (I have 4 of these)

$fieldX = [string]([Math]::Round((($dskYYY | Measure-Object Value -Average).Average),2))

I'm unfortunately getting 0 for all of these stats.  My level settings are all set at 2.  It would be great if I could receive assistance regarding this.