Check Free Disk Space with PowerShell

# Check Disk Space
# Single use case: report free space on all fixed volumes, warn below threshold
# Author: SENTRI AI Engine | Date: 2026.08.14
#-----------------------------------------------------------------

function Write-Log {
    param(
        [Parameter(Mandatory)]
        [string]$Message,

        [ValidateSet('INFO', 'WARN', 'ERROR', 'OK')]
        [string]$Level = 'INFO'
    )
    $prefix = switch ($Level) {
        'WARN'  { '[WARN]  ' }
        'ERROR' { '[ERROR] ' }
        'OK'    { '[OK]    ' }
        default { '[INFO]  ' }
    }
    Write-Host "<WRITE-LOG = `"*$prefix$Message*`">"
}

# --- Parameters (replace via ServerEngine API parameters if needed) ---
$WarnPercentFree = 15
$WarnAbsoluteGB  = 5.0   # Also warn if less than this many GB are free, regardless of percentage

$volumes = Get-CimInstance -ClassName Win32_LogicalDisk -Filter "DriveType=3" -ErrorAction SilentlyContinue
if (-not $volumes) {
    Write-Log "No fixed volumes found!" -Level ERROR
    return
}

$warnings = 0
$hostname = $env:COMPUTERNAME
Write-Log "================ Disk Space Report — $hostname ================"
foreach ($v in $volumes) {
    if ($v.Size -eq 0) { continue }
    $freeGB  = [math]::Round($v.FreeSpace / 1GB, 2)
    $sizeGB  = [math]::Round($v.Size / 1GB, 2)
    $usedGB  = [math]::Round(($v.Size - $v.FreeSpace) / 1GB, 2)
    $freePct = [math]::Round(($v.FreeSpace / $v.Size) * 100, 1)

    $belowPercent = $freePct -lt [double]$WarnPercentFree
    $belowAbsolute = $freeGB -lt $WarnAbsoluteGB

    if ($belowPercent -or $belowAbsolute) {
        $reasons = @()
        if ($belowPercent) { $reasons += "free space $freePct% below ${WarnPercentFree}% threshold" }
        if ($belowAbsolute) { $reasons += "absolute free space ${freeGB} GB below ${WarnAbsoluteGB} GB minimum" }
        Write-Log "WARNING: [$($v.DeviceID)] $freeGB GB free of $sizeGB GB (${usedGB} GB used, $freePct% free) — $($reasons -join '; ')" -Level WARN
        $warnings++
    } else {
        Write-Log "OK: [$($v.DeviceID)] $freeGB GB free of $sizeGB GB ($freePct% free)" -Level OK
    }
}

Write-Log "Disk space scan complete: $warnings volume(s) flagged." -Level $(if ($warnings -gt 0) { 'WARN' } else { 'OK' })