Monitoring disk space is a basic but core component of proactive IT support, critical to reducing ticket volume and maintaining system health and stability. Running low on or running out of disk space can obviously be responsible for a host of issues and user complaints — from application failures to complete system crashes — so creating alerts for when drives fall below a specified threshold is a great way to head those off.
This post will walk you through how to check disk capacity and alert on low disk space remotely, across your entire user base.
How can I check hard drive space remotely and send an alert when disk space is low?
- Identify which drives you want to monitor and which (if any) you want to exclude.
- Determine the disk space thresholds you would like to set for each type of drive.
- Customize the script below, accordingly.
This PowerShell script is designed to alert on drive(s) that fall below a specified percentage or size. It distinguishes between system drives (those used to boot the OS) and data drives, providing a comprehensive overview of your disk space usage.
The script is versatile and customizable, allowing you to set parameters for system and data drives separately. You can specify the minimum free space in both percentage and bytes, and even exclude certain drives from the check. This flexibility is ideal for any IT professional or MSP.
The Disk Space Monitor Script:
#Requires -Version 2.0
<#
.SYNOPSIS
Alert on drive(s) that fall below a specified % or size. Distinguishes between System and Data drives.
.DESCRIPTION
Alert on drive(s) that fall below a specified % or size. Distinguishes between System and Data drives.
The system drive is the drive(s) that are used to boot the OS.
.EXAMPLE
-SystemDriveMinFreePercent 10 -SystemDriveMinFreeBytes 10GB -DataDriveMinFreePercent 20 -DataDriveMinFreeBytes 20GB
This checks all Drives
.EXAMPLE
-ExcludeDrivesCustomField "C,Z" -SystemDriveMinFreePercentCustomField "SystemDriveMinFreePercent" -SystemDriveMinFreeBytes "SystemDriveMinFreeBytes" -DataDriveMinFreePercent "DataDriveMinFreePercent" -DataDriveMinFreeBytes "DataDriveMinFreeBytes"
This checks all Drives, except for C: and Z:.
Use this if you wish to to custom fields to specify the values from roles or globally.
This will pull the values from custom fields that would have otherwise been used from parameters.
.EXAMPLE
-ExcludeDrivesByNameCustomField "NoMonitor" -SystemDriveMinFreePercentCustomField "SystemDriveMinFreePercent" -SystemDriveMinFreeBytes "SystemDriveMinFreeBytes" -DataDriveMinFreePercent "DataDriveMinFreePercent" -DataDriveMinFreeBytes "DataDriveMinFreeBytes"
This checks all Drives, except where a drive name/label contains the text "NoMonitor".
Use this if you wish to to custom fields to specify the values from roles or globally.
This will pull the values from custom fields that would have otherwise been used from parameters.
.EXAMPLE
No Parameters Specified
This checks all Drives with the defaults:
SystemDriveMinFreePercent 10%
SystemDriveMinFreeBytes 10GB
DataDriveMinFreePercent 20%
DataDriveMinFreeBytes 20GB
.OUTPUTS
None
.NOTES
Minimum OS Architecture Supported: Windows 7, Windows Server 2012 R2
Release Notes:
Initial Release
(c) 2023 NinjaOne
By using this script, you indicate your acceptance of the following legal terms as well as our Terms of Use at https://www.ninjaone.com/terms-of-use.
Ownership Rights: NinjaOne owns and will continue to own all right, title, and interest in and to the script (including the copyright). NinjaOne is giving you a limited license to use the script in accordance with these legal terms.
Use Limitation: You may only use the script for your legitimate personal or internal business purposes, and you may not share the script with another party.
Republication Prohibition: Under no circumstances are you permitted to re-publish the script in any script library or website belonging to or under the control of any other software provider.
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Waiver and Release: You will not hold NinjaOne responsible for any adverse or unintended consequences resulting from your use of the script, and you waive any legal or equitable rights or remedies you may have against NinjaOne relating to your use of the script.
EULA: If you are a NinjaOne customer, your use of the script is subject to the End User License Agreement applicable to you (EULA).
#>
[CmdletBinding()]
param (
[Parameter()]
[String]
$ExcludeDrives,
$ExcludeDrivesCustomField, # If set, get value from a custom field with this name.
[String]
$ExcludeDrivesByName,
$ExcludeDrivesByNameCustomField, # If set, get value from a custom field with this name.
$SystemDriveMinFreePercent = 10,
$SystemDriveMinFreePercentCustomField, # If set, get value from a custom field with this name.
$SystemDriveMinFreeBytes = 10GB,
$SystemDriveMinFreeBytesCustomField, # If set, get value from a custom field with this name.
$DataDriveMinFreePercent = 20,
$DataDriveMinFreePercentCustomField, # If set, get value from a custom field with this name.
$DataDriveMinFreeBytes = 20GB,
$DataDriveMinFreeBytesCustomField # If set, get value from a custom field with this name.
)
begin {
function Get-Size {
param (
[string]$String
)
switch -wildcard ($String) {
'*PB' { [int64]$($String -replace '[^d+]+') * 1PB; break }
'*TB' { [int64]$($String -replace '[^d+]+') * 1TB; break }
'*GB' { [int64]$($String -replace '[^d+]+') * 1GB; break }
'*MB' { [int64]$($String -replace '[^d+]+') * 1MB; break }
'*KB' { [int64]$($String -replace '[^d+]+') * 1KB; break }
'*B' { [int64]$($String -replace '[^d+]+') * 1; break }
'*Bytes' { [int64]$($String -replace '[^d+]+') * 1; break }
Default { [int64]$($String -replace '[^d+]+') * 1 }
}
}
function Get-FriendlySize {
param($Bytes)
# Converts Bytes to the highest matching unit
$Sizes = 'Bytes,KB,MB,GB,TB,PB,EB,ZB' -split ','
for ($i = 0; ($Bytes -ge 1kb) -and ($i -lt $Sizes.Count); $i++) { $Bytes /= 1kb }
$N = 2
if ($i -eq 0) { $N = 0 }
if ($Bytes) { "$([System.Math]::Round($Bytes,$N)) $($Sizes[$i])" }else { "0 B" }
}
function Invoke-DiskAlert {
param (
[PSObject[]]$Drives
)
$Drives | ForEach-Object {
$Type = if ($_.IsSystemDrive) { "SystemDrive" }else { "DataDrive" }
$Drive = $_
if ($Drive.totalSpace -and $Drive.freeSpace / $Drive.totalSpace * 100 -lt $Settings."$Type".MinFreePercent) {
Write-Output "$Type ($($Drive.driveName)) free space is under $($Settings."$Type".MinFreePercent)% at $(Get-FriendlySize -Bytes $Drive.freeSpace)"
}
elseif ($Drive.freeSpace -lt $Settings.$Type.MinFreeBytes) {
Write-Output "$Type ($($Drive.driveName)) free space is under $(Get-FriendlySize -Bytes $Settings."$Type".MinFreeBytes) at $(Get-FriendlySize -Bytes $Drive.freeSpace)"
}
}
}
function Get-Drive {
param([string]$DriveName)
if ($(Get-Command -Name "Get-CimInstance")) {
Get-CimInstance -Query "select * from Win32_DiskDrive" | Where-Object { $_.Size } | ForEach-Object {
$d = $_
$d | ForEach-Object {
$Disk = $_
$p = Get-CimInstance -Query "ASSOCIATORS OF {Win32_DiskDrive.DeviceID='$($Disk.DeviceID)'} WHERE AssocClass = Win32_DiskDriveToDiskPartition"
$p | ForEach-Object {
$Partition = $_
Get-CimInstance -Query "ASSOCIATORS OF {Win32_DiskPartition.DeviceID='$($Partition.DeviceID)'} WHERE AssocClass = Win32_LogicalDiskToPartition" | ForEach-Object {
$ld = $_
[PSCustomObject]@{
driveName = $ld.DeviceId # C:
IsSystemDrive = if ($p | Where-Object { $_.BootPartition }) { $true }else { $false }
freeSpace = $ld.FreeSpace # in bytes
totalSpace = $ld.Size # in bytes
fileSystem = $ld.FileSystem # NTFS
physicalName = $d.Name # .PHYSICALDRIVE2
diskName = $d.Caption # WDC WD5001AALS-xxxxxx
diskModel = $d.Model # WDC WD5001AALS-xxxxxx
diskInterface = $d.InterfaceType # IDE
mediaStatus = $d.Status # OK
volumeName = $ld.VolumeName # System
volumeSerial = $ld.VolumeSerialNumber # 12345678
}
}
}
}
}
}
else {
Get-WmiObject -Query "select * from Win32_DiskDrive" | Where-Object { $_.Size } | ForEach-Object {
$d = $_
$d | ForEach-Object {
$Disk = $_
$p = Get-WmiObject -Query "ASSOCIATORS OF {Win32_DiskDrive.DeviceID='$($Disk.DeviceID)'} WHERE AssocClass = Win32_DiskDriveToDiskPartition"
$p | ForEach-Object {
$Partition = $_
Get-WmiObject -Query "ASSOCIATORS OF {Win32_DiskPartition.DeviceID='$($Partition.DeviceID)'} WHERE AssocClass = Win32_LogicalDiskToPartition" | ForEach-Object {
$ld = $_
[PSCustomObject]@{
driveName = $ld.DeviceId # C:
IsSystemDrive = if ($p | Where-Object { $_.BootPartition }) { $true }else { $false }
freeSpace = $ld.FreeSpace # in bytes
totalSpace = $ld.Size # in bytes
fileSystem = $ld.FileSystem # NTFS
physicalName = $d.Name # .PHYSICALDRIVE2
diskName = $d.Caption # WDC WD5001AALS-xxxxxx
diskModel = $d.Model # WDC WD5001AALS-xxxxxx
diskInterface = $d.InterfaceType # IDE
mediaStatus = $d.Status # OK
volumeName = $ld.VolumeName # System
volumeSerial = $ld.VolumeSerialNumber # 12345678
}
}
}
}
}
}
}
}
process {
# Get values from parameters
$Settings = [PSCustomObject]@{
SystemDrive = [PSCustomObject]@{
MinFreePercent = if ($env:SystemDriveMinFreePercent) { $env:SystemDriveMinFreePercent -replace '%' }else { $SystemDriveMinFreePercent }
MinFreeBytes = if ($env:SystemDriveMinFreeBytes) { Get-Size -Size $env:SystemDriveMinFreeBytes }else { $SystemDriveMinFreeBytes }
}
DataDrive = [PSCustomObject]@{
MinFreePercent = if ($env:DataDriveMinFreePercent) { $env:DataDriveMinFreePercent -replace '%' }else { $DataDriveMinFreePercent }
MinFreeBytes = if ($env:DataDriveMinFreeBytes) { Get-Size -Size $env:DataDriveMinFreeBytes }else { $DataDriveMinFreeBytes }
}
}
# Get values from custom field
if ($SystemDriveMinFreePercentCustomField) {
$Settings.SystemDrive.MinFreePercent = Ninja-Property-Get -Name $SystemDriveMinFreePercentCustomField
}
if ($SystemDriveMinFreeBytesCustomField) {
$Settings.SystemDrive.MinFreeBytes = Ninja-Property-Get -Name $SystemDriveMinFreeBytesCustomField
}
if ($DataDriveMinFreePercentCustomField) {
$Settings.DataDrive.MinFreePercent = Ninja-Property-Get -Name $DataDriveMinFreePercentCustomField
}
if ($DataDriveMinFreeBytesCustomField) {
$Settings.DataDrive.MinFreeBytes = Ninja-Property-Get -Name $DataDriveMinFreeBytesCustomField
}
if ($env:ExcludeDrives) {
$ExcludeDrives = $env:ExcludeDrives
}
if ($ExcludeDrivesCustomField) {
$ExcludeDrives = Ninja-Property-Get -Name $ExcludeDrivesCustomField
}
if ($env:ExcludeDrivesByName) {
$ExcludeDrivesByName = $env:ExcludeDrivesByName
}
if ($env:ExcludeDrivesByNameCustomField) {
$ExcludeDrivesByNameCustomField = $env:ExcludeDrivesByNameCustomField
}
# System.IO.DriveInfo is usable as far back as .NET 2.0 for Windows 7 compatibility.
# Reference: https://learn.microsoft.com/en-us/dotnet/api/system.io.driveinfo?view=netstandard-2.0
# Get drives that are in the ready state
$Drives = Get-Drive
$Results = if ($Drives) {
$DrivesFiltered = if ($ExcludeDrivesByName) {
$Drives | Where-Object { $_.volumeName -notlike "*$ExcludeDrivesByName*" }
}
else { $Drive }
if ($ExcludeDrives) {
$DriveAlerts = Invoke-DiskAlert -Drives $DrivesFiltered
$DriveList = if ($ExcludeDrives -like "*,*") {
$ExcludeDrives -split ',' | Sort-Object -Unique
}
else {
$ExcludeDrives -split '' | Sort-Object -Unique | Select-Object -Skip 1
}
$DriveList | ForEach-Object {
$Drive = $_
$DriveAlerts | Where-Object { $_ -notlike "*$($Drive):*" }
}
}
else {
Invoke-DiskAlert -Drives $Drives $DrivesFiltered
}
}
else {
# Should never get here, how was the script executed?!
"No drives found?!" | Out-String | Write-Host
exit 2
}
if ($Results) {
$Results | Out-String | Write-Host
exit 1
}
else {
Write-Host "No drives found with low free space."
exit 0
}
}
end {
$ScriptVariables = @(
[PSCustomObject]@{
name = "Exclude Drives"
calculatedName = "excludedrives"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "List if mounted drives to exclude from low drive check. Example: CFZ or C,F,Z"
}
[PSCustomObject]@{
name = "Exclude Drives Custom Field"
calculatedName = "excludedrivescustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. List if mounted drives to exclude from low drive check. Example: CFZ or C,F,Z"
}
[PSCustomObject]@{
name = "Exclude Drives By Name"
calculatedName = "excludedrivesbyname"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "Exclude drives with with the specified text in it's name/label."
}
[PSCustomObject]@{
name = "Exclude Drives By Name Custom Field"
calculatedName = "excludedrivesbynamecustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. Exclude drives with with the specified text in it's name/label."
}
[PSCustomObject]@{
name = "System Drive Minimum Size in Percent"
calculatedName = "systemdriveminfreepercent"
required = $false
defaultValue = [PSCustomObject]@{
type = "TEXT"
value = "10%"
}
valueType = "TEXT"
valueList = $null
description = "The percentage of free space to alert on when the OS drive is below this percentage. Example: 50 or 50%"
}
[PSCustomObject]@{
name = "System Drive Minimum Size in Bytes"
calculatedName = "systemdriveminfreebytes"
required = $false
defaultValue = [PSCustomObject]@{
type = "TEXT"
value = "10GB"
}
valueType = "TEXT"
valueList = $null
description = "The minimum free space to alert on when the OS drive is below this amount. Example: 50GB, 50000MB, or 53687091200"
}
[PSCustomObject]@{
name = "Data Drive Minimum Size in Percent"
calculatedName = "datadriveminfreepercent"
required = $false
defaultValue = [PSCustomObject]@{
type = "TEXT"
value = "20%"
}
valueType = "TEXT"
valueList = $null
description = "The percentage of free space to alert on when a Data drive is below this percentage. Example: 50 or 50%"
}
[PSCustomObject]@{
name = "Data Drive Minimum Size in Bytes"
calculatedName = "datadriveminfreebytes"
required = $false
defaultValue = [PSCustomObject]@{
type = "TEXT"
value = "20GB"
}
valueType = "TEXT"
valueList = $null
description = "The minimum free space to alert on when the Data drive is below this amount. Example: 50GB, 50000MB, or 53687091200"
}
[PSCustomObject]@{
name = "System Drive Minimum Size in Percent Custom Field"
calculatedName = "systemdriveminfreepercentcustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. The percentage of free space to alert on when the OS drive is below this percentage. Example: 50 or 50%"
}
[PSCustomObject]@{
name = "System Drive Minimum Size in Bytes Custom Field"
calculatedName = "systemdriveminfreebytescustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. The minimum free space to alert on when the OS drive is below this amount. Example: 50GB, 50000MB, or 53687091200"
}
[PSCustomObject]@{
name = "Data Drive Minimum Size in Percent Custom Field"
calculatedName = "datadriveminfreepercentscustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. The percentage of free space to alert on when a Data drive is below this percentage. Example: 50 or 50%"
}
[PSCustomObject]@{
name = "Data Drive Minimum Size in Bytes Custom Field"
calculatedName = "datadriveminfreebytescustomfield"
required = $false
defaultValue = $null
valueType = "TEXT"
valueList = $null
description = "A custom field to get the value from. The minimum free space to alert on when the Data drive is below this amount. Example: 50GB, 50000MB, or 53687091200"
}
)
$ScriptName = "Condition Low Disk Space Alert"
}
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How the Disk Space Monitor Script Works
The script works by first gathering information about all the drives on the system. It then filters out any drives you’ve chosen to exclude and checks the remaining ones against the parameters you’ve set. If any drive falls below the specified minimum free space, the script will alert you, allowing you to take action before it becomes a problem.
One of the standout features of this script is its ability to pull values from custom fields. This means you can specify values globally or from roles, adding another layer of customization to the script.
Transforming IT Management with NinjaOne
While it’s possible to monitor disk space strictly using PowerShell from a local computer, there’s an even better way to manage your IT resources, remotely and at scale — NinjaOne.
NinjaOne is a unified IT management platform that incorporates remediation steps, using scripts if needed, into highly flexible device policies that determine when alert thresholds are met and the subsequent steps that should be taken. NinjaOne provides access to hundreds of scripts that you may find useful, and the ability to create your own in nearly any scripting language.
NinjaOne can help you monitor and manage all your IT endpoints at scale from a single dashboard. With policies and scripts, you can automate virtually any routine task from installing software patches to generating reports, saving time and proactively managing issues before they become problems.