##Parameter
$NUMBER_OF_SAMPLES = 5;
$SAMPLE_INTERVAL_TIME = 1;
###Load server list
$serverList = Get-Content -Path C:\temp\server.txt;
##Defining the counter and threshold values
##Each line: Counter, alarm triggers if over/under, threshold value
$counters = (
('\Memory\Available MBytes', 'under', 500), #Alert if under 500
('\Processor(_Total)\% Processor Time', 'over', 60), #Alert if over 60
('\LogicalDisk(_Total)\% Free Space', 'under', 10 ) #Alert if under 10
) #Array end
function checkLowerLimit([int]$threshold, [int]$average)
{
    if($average -lt $threshold)
   {
      Write-Host "threshold value not reached!" return $false;
    }
    return $true;
}
function checkUpperLimit([int]$threshold, [int]$average)
{
    if($average -gt $threshold)
    {
      Write-Host "threshold value exceeded!" return $false;
    }
    return $true;
}
function getPerformanceData([array]$counter, [string]$machine)
{
    try
    {
      $v = Get-Counter -Counter $counter -ComputerName $machine -MaxSamples $NUMBER_OF_SAMPLES -SampleInterval
      $SAMPLE_INTERVAL_TIME -ErrorAction SilentlyContinue
      if($v -eq $null -or $v -eq "")
      {
        Write-Host "Counter $($counter) delivered no value."
        Continue;
      }
      $average = ($v.CounterSamples.CookedValue | Measure-Object -Average).Average
    }
    catch
    {
      Write-Host "Error: the counter could not be collected. Reason: $($_)"
    }
    ##Bigger or smaller?
    if($counter[1] -eq "under") { $limit = checkLowerLimit $counter[2] $average }
    else { $limit = checkUpperLimit $counter[2] $average }
    ##If the test retruns a "$false", the threshold value has been damaged:
    if(-not $limit) { Write-Host "[$($machine)] Counter $($counter[0]) has, with the value $($average),
    exceed $($counter[2]) not reached $($counter[1]) the threshold value." }
}
###The script starts here:
$c = $serverlist.Count * $counters.Count
$i=0;
foreach($server in $serverList)
{
    foreach($counter in $counters)
    {
      Write-Progress -activity "Collecting performance data" -status "Counter data $($i+1) from $($c):
      $($counter) on $($server)" -PercentComplete $(($i+1)/($c)*100)
      getPerformanceData $counter $server
      $i++;
    }
} #End foreach server
    Write-Host "End of the collection. Threshold limit damages are issued on the command line."