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How can I monitor free disk space of LUNs in a XEN pool?



In order to keep an eye on disk space usage, I want to monitor LUNs and local storage of my Xen pool and Xen server. Unfortunately, the SSH Disk Free sensor only works with CIFS and NFS, but not with iSCSI shares.

Is there another way to monitor free disk space of iSCSI shares?

disk-free free-disk-space iscsi lun prtg share xen xenpool xenserver

Created on Dec 19, 2013 12:56:47 PM by  Gerald Schoch [Paessler Support]

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Accepted Answer



This article applies to PRTG Network Monitor 13 or later

Monitoring Free Disk Space on a LUN of an iSCSI Target

Free disk space on a LUN (logical unit number) which represents an individually addressable logical iSCSI (Internet Small Computer System Interface) device cannot be monitored with the SSH Disk Free sensor. The reason is that the df command does not show these iSCSI targets. Though, you can still monitor NFS (Network File System) and CIFS (Common Internet File System) with this sensor type.

Monitoring iSCSI LUNs Using a Script

If a percentage value for free disk space on a LUN is sufficient for you, you can monitor this number in PRTG with an SSH Script Sensor. Please follow the steps below.

1. Create a script with the following content:


xe sr-list uuid=$1 params=physical-utilisation,physical-size | awk '{if (NR == 1) {pu = $NF}; if (NR == 2) {ps = $NF; print "0:" pu/ps*100 ":OK"}}'

2. Save it in the /var/prtg/scripts folder on the target system (i.e., on the Xen server). 3. Make the file executable with the change owner command:

chown <user> <script>

4. Determine the UUID (Universally Unique Identifier) of the iSCSI target on the Xen server. Use the following command to get a list of UUIDs of connected targets:

xe sr-list name-label='iSCSI storage' --minimal

5. For each listed UUID, create an SSH Script sensor in PRTG.

  1. Open the Add Sensor dialog in PRTG und select SSH Script.
  2. Select the created script from the drop list.
  3. Choose value type Float.
  4. As parameter, enter the particular UUID.
  5. Optionally, after sensor creation, open the settings of the Value channel. Enter % in the Unit field and choose Custom in section Decimal Places (you can leave the default value 2).

With these settings, the created sensor will show the free space on a particular LUN in percent.

Feel free to adjust the given script to your needs. Please consider the correct format for the returned data, see PRTG Manual: Custom Sensors for more information.

See Also

If you encounter wrong disk usage data, please see the following article in the Citrix Knowledge Center: XenCenter Shows Incorrect Usage Data

Created on Dec 19, 2013 1:01:33 PM by  Gerald Schoch [Paessler Support]

Last change on Aug 10, 2018 12:12:59 PM by  Brandy Greger [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.