Monday, April 6, 2009

Logical Disk Free Space Monitor & the three most common misunderstandings...

The Server OS MP contains many usefull monitors. One of these monitors is the one which checks the available free space of the logical disks. But there are some misunderstandigs about this monitor. And to be frankly, when the document included with this MP is properly read, most of these misunderstandings wouldn’t occur.
So RTFM (Read The Friendly Manual) before importing any MP...
The most common mistakes are:

1: Two values are being used by this monitor, not one.
This monitor uses TWO values to reflect the state: the percentage of available free diskspace AND the available MBs of free diskspace. Based on the outcome of both values this monitor will generate an alert. So when one of these values is well within the range where an alert will not be triggered, SCOM will not raise an alert.

Both values have to fall within a certain range before an Alert is raised. Ofcourse these values can be adjusted to a level which matches the monitored environment.

2: Only critical alerts are being shown, not the warnings.
Normally this monitor shows only a critical alert in the Alertview of SCOM, not a warning. This is by design. But what if one likes to get an warning when the disk is becoming almost too full so there is more time to (re)act?

For this an override is needed. Follow this easy procedure and a Warning like this screendump will be displayed in the Alertview of SCOM:

  • Go to Tools, Search, Monitors.
  • In the Searchbox type Logical Disk Free Space and hit enter.
  • In the Monitor Details pane a link named View Knowledge appears. Click it.
  • Go to the tab Overrides and click the button Override.
  • Select the first option For all objects of type: Windows Server Logical Disk.
  • Place a checkmark at the option Alert On State.
  • Change the option in the column Override Setting to The monitor is in a critical or warning state.
  • Save the changes into a NEW MP. Click Apply, OK.

Now one has more time to act.

3: Timeframe the monitor runs.
Sometimes customers complain the monitored disks ended up full without SCOM raising an alert in a timely fashion. But that is by design since this monitors runs once every hour. With an override this can be easily adjusted.

Follow the earlier mentioned procedure but at step 5 one must select For a specific object of type: Windows Server 200x Logical Disk. Select the server and disk for which the monitor needs to be altered. Then one adjusts the value of the row Interval (seconds) to a value that fits the scenario one is aiming at. Save your changes into a NEW MP and all is well again.


Dominique said...

What an excellent blog it is....


Marnix Wolf said...