What is this?

This knowledgebase contains questions and answers about PRTG Network Monitor and network monitoring in general.

Learn more

PRTG Network Monitor

Intuitive to Use. Easy to manage.
More than 500,000 users rely on Paessler PRTG every day. Find out how you can reduce cost, increase QoS and ease planning, as well.

Free Download

Top Tags

View all Tags

Disk Free Sensor (Windows SNMP) maxed out at 16,34GB



Dear Community,

I want to monitor the free disk space on a 50TB drive that exists on our backup server. Sadly the DiskFree sensor SNMP always shows 100% free and 16.777.216 MB free. But it should be more.

I also notice that it does not recognize the actual max size of 50TB. Not even when I change it to GB or TB.

How can I monitor bigger drives than 16TB or why is this error happening. Can anyone help?

disk-free prtg snmp

Created on Sep 14, 2021 2:05:11 PM

1 Reply




Thank you for your message.

To investigate on the origin of the issue, can you please provide me the following:

  • Allocation unit size of the disk (via PowerShell console by using the command below)
Get-CimInstance -ClassName Win32_Volume | Select-Object Label, BlockSize | Format-Table -AutoSize
  • Result of a walk on the OID "" with SNMP Tester

How to use the tester:

  1. Start the SNMP Tester
  2. Configure the tester below point "1. Set SNMP Settings"
    1. Local IP = Any (at first). If this fails, also switch to one of the listed local IPs
    2. Device IP/Port = IP of the target device and the configured port (SNMP uses port 161 by default)
    3. SNMP Version = Select the version which is configured on the device
    4. Community = Community string defined in the target device
  3. Below "Select Request Type", switch to the option "Walk" and copy the OID provided above
  4. Press the "Start" Button on the top

If the output is quite long, I invite you to use an external service like pastebin to store it temporarily and provide a link. Otherwise, you can add it directly in your response.


Created on Sep 15, 2021 6:20:31 AM by  Florian Lesage [Paessler Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.