Powershell Script - Send Email Only When Drive Space Is Below MinThreshold

Question

I'm using Windows 10 Enterprise 1709 and PowerShell version 5.0. I have this PowerShell script below that I found online. It works but I don't understand what a line in code is doing so I can decided how to edit it for what I need to do. Also, it sends an email even though the drive is not below minimum threshold. I would like to understand this line of the code and fix it to only send email alert when it reaches below the minimum threshold. $freeSpaceGB = [Math]::Round([float]$disk.FreeSpace / 1073741824);and this line $computer = $computer.toupper();

The entire code is below:

$minGbThreshold = 50GB

$computers = $env:COMPUTERNAME
$smtpAddress = "smtp.anydomain.com"
$toAddress = "[e-mail]"
$fromAddress = "[e-mail]"

foreach($computer in $computers)
{    
    $disks = Get-WmiObject -ComputerName $computer -Class Win32_LogicalDisk -Filter "DriveType = 3";
    $computer = $computer.toupper();
    $deviceID = $disk.DeviceID;
    foreach($disk in $disks)
    {
        $freeSpaceGB = [Math]::Round([float]$disk.FreeSpace / 1073741824);
        if($freeSpaceGB -lt $minGbThreshold)
        {
            $smtp = New-Object Net.Mail.SmtpClient($smtpAddress)
            $msg = New-Object Net.Mail.MailMessage
            $msg.To.Add($toAddress)
            $msg.From = $fromAddress
            $msg.Subject = “Diskspace below threshold ” + $computer + "\" + $disk.DeviceId
            $msg.Body = $computer + "\" + $disk.DeviceId + " " + $freeSpaceGB + "GB Remaining";
            $smtp.Send($msg)
        }
    }
}

Answer 1

$freeSpaceGB = [Math]::Round([float]$disk.FreeSpace / 1073741824);

Determines the amount of free storage space the HDD has in Gigabytes (GB) to the nearest GB.

1,073,741,824 bytes is 1.073741824 Gigabytes which is the amount of bytes that Windows uses to indicate a single Gigabyte (GB).

2^30 = 1,073,741,824

The gibibyte is a multiple of the unit byte for digital information. The binary prefix gibi means 230, therefore one gibibyte is equal to 1073741824 bytes.

Source: Gibibyte

$computer = $computer.toupper();

Simply changes to the case of the name of the computer to all uppercase.

I still need to understand why I still get an email even though the disk space isn't below the minimum

$minGbThreshold = 50GB
$freeSpaceGB = [Math]::Round([float]$disk.FreeSpace / 1073741824);

The integer value of 57 is indeed less than the alphanumeric value of the string 50GB.

Explanation:

61,717,860,352 / 1,073,741,824 = 57.4792

57.4792 would round down to a integer value of 57

The original snippet actually indicated the correct value for $minGbThreshold.

$minGbThreshold = 25

Source: Automated Disk Space Alerts For Windows Server