DiskQueueMonitor.ps1

param(
    [int]$DurationSeconds = 60,
    [int]$IntervalSeconds = 5
)

function Get-DiskQueueAverages {
    param(
        [int]$DurationSeconds,
        [int]$IntervalSeconds
    )

    $sampleCount = [math]::Max(1, [int]($DurationSeconds / $IntervalSeconds))
    $counterCandidates = @('\PhysicalDisk(*)\Avg. Disk Queue Length', '\LogicalDisk(*)\Avg. Disk Queue Length')

    $resultSets = $null
    $usedCounter = $null
    foreach ($path in $counterCandidates) {
        try {
            $resultSets = Get-Counter -Counter $path -SampleInterval $IntervalSeconds -MaxSamples $sampleCount -ErrorAction Stop
            $usedCounter = $path
            break
        } catch {
            $resultSets = $null
        }
    }

    if (-not $resultSets) {
        throw "Failed to read disk queue length counters. Tried: $($counterCandidates -join ', ')."
    }

    $valuesByInstance = @{}
    foreach ($set in $resultSets) {
        foreach ($cs in $set.CounterSamples) {
            $inst = $cs.InstanceName
            if (-not $inst -or $inst -eq '_Total') { continue }
            if (-not $valuesByInstance.ContainsKey($inst)) { $valuesByInstance[$inst] = @() }
            $valuesByInstance[$inst] += [double]$cs.CookedValue
        }
    }

    $averages = foreach ($kv in $valuesByInstance.GetEnumerator()) {
        $avg = if ($kv.Value.Count) { ($kv.Value | Measure-Object -Average).Average } else { 0 }
        [PSCustomObject]@{ Instance = $kv.Key; Average = [Math]::Round([double]$avg, 4) }
    }

    [PSCustomObject]@{
        CounterPath     = $usedCounter
        IntervalSeconds = $IntervalSeconds
        DurationSeconds = $DurationSeconds
        SampleCount     = $sampleCount
        Results         = $averages | Sort-Object Instance
    }
}

try {
    $data = Get-DiskQueueAverages -DurationSeconds $DurationSeconds -IntervalSeconds $IntervalSeconds

    $logPath = Join-Path -Path $PSScriptRoot -ChildPath 'disk_queue_log.txt'
    $ts = Get-Date -Format o
    $lines = @()
    $lines += "==== Disk Queue Monitor Run ===="
    $lines += "Timestamp: $ts"
    $lines += "Counter: $($data.CounterPath)"
    $lines += "Interval: $($data.IntervalSeconds)s  Duration: $($data.DurationSeconds)s  Samples: $($data.SampleCount)"
    foreach ($row in $data.Results) {
        $lines += ("{0,-20} avg={1}" -f $row.Instance, $row.Average)
    }
    $lines += ""
    $lines | Out-File -FilePath $logPath -Encoding utf8 -Append

    Write-Host "Average 'Avg. Disk Queue Length' over $($data.DurationSeconds)s (every $($data.IntervalSeconds)s):" -ForegroundColor Cyan
    $data.Results | Sort-Object Average -Descending | Format-Table -AutoSize Instance, Average
    Write-Host "Logged details to: $logPath" -ForegroundColor DarkGray
}
catch {
    Write-Error $_
    exit 1
}