Server OS MP version 6.0.6972.0: New Logical Disk Free Space Monitoring Explained

With the latest version of the Server OS MP, version 6.0.6972.0, the monitoring of the free space on the logical disks of those servers is changed as well. Even though Kevin Holman wrote an excellent posting about those changes, I bump into customers asking many questions about those changes.

This posting is a wrap-up of those changes. However, all credits for this posting should go to Kevin since this posting is based on his article.

The 3 Logical Disk Free Space Monitors
When the latest version of the Server OS MP is imported, you’ll find per Server OS type (2003/2008) three Monitors for monitoring the logical disk free space. In this screen dump I only have the Server OS MP for Windows Server 2008 imported so only those three Monitors are shown:

Let’s break them down:

01: Logical Disk Free Space

1. This is the monitor we all know from all previous Server OS MPs. One per Server OS type (2003/2008).
2. This Monitor is rewritten in order to reduce noise, but…
   • Now the Alerts don’t show anymore how many MBs and percent of free space is still available;
   • In order to address that, Kevin and Larry Mosley created addendum MPs containing the previous versions of those Monitors and disable the newest versions. The blog posting about the new Monitors and also containing the addendum MPs can be found here.
3. This monitor is enabled by default in order to guarantee backward compatibility for organizations who have SCOM/OM12 for some time in place. Many times  organizations like these do have many overrides in place for this monitor.
4. Things to reckon with this Monitor:
   • It measures two conditions: available free space measured in MBs AND percentage. Only when BOTH conditions are met an Alert will be triggered!
   • By default it will trigger an Alert when it’s in a Warning or Critical state. Even though it might sound good there is a drawback here: Suppose a Warning Alert is triggered for a certain logical disk because the free space is too low but yet not critical. So a Warning Alert is shown in the Console. When the amount of free space becomes critical the current Warning Alert will be set to a Critical state. This WON’T create a new Alert nor will a notification be send out, nor will it be picked up by any Connector (if in place) to any Service Desk tool…
5. This Monitor runs every 15 minutes
   

02: Windows Server 2008 Logical Disk Free Space (%) Low

1. This is a new Monitor introduced in this version of the Server OS MP;
2. This Monitor is disabled by default;
3. This Monitor only raises an Alert when ONE condition is met: when the percentage of free disk space is below a certain level;
4. This Monitor only raises an Alert when a CRITICAL condition is met;
5. This Monitor runs every 15 minutes;
6. The Alert generated by this Monitor also shows the percentage of free space left;
7. This Monitor can be customized on many Parameters in order to reflect the requirements of your organization:
   
   Advice: Don’t change the Alert on State parameter since you’ll bump into the same issue as described for the Logical Disk Free Space monitor, Item 4, second bullet…
   

03: Windows Server 2008 Logical Disk Free Space (MB) Low

1. This is a new Monitor introduced in this version of the Server OS MP;
2. This Monitor is disabled by default;
3. This Monitor only raises an Alert when ONE condition is met: when the amount of free MBs is below a certain level;
4. This Monitor only raises an Alert when a CRITICAL condition is met;
5. This Monitor runs every 15 minutes;
6. The Alert generated by this Monitor also shows the amount of free MBs left;
7. This Monitor can be customized on many Parameters in order to reflect the requirements of your organization:
   
   Advice: Don’t change the Alert on State parameter since you’ll bump into the same issue as described for the Logical Disk Free Space monitor, Item 4, second bullet…

OK, now what monitor do I use?
This is up to you, or better the requirements of your organization. Personally I wouldn’t be too much surprised to see the monitor Logical Disk Free Space to be phased out in a future version of the Server OS MP. But these are just my personal thoughts and isn’t based on anything else.

When you have a SCOM R2/OM12 MG in place with many overrides for the Logical Disk Free Space Monitor, it isn’t that easy to move to ONE of the new Monitors. Planning is required here.

Tips & Tricks for the Logical Disk Free Space Monitor

1. Another approach could be to to alter the Logical Disk Free Space Monitor so one of the two conditions (percentage or amount of free MBs) is already in a warning/critical state. This way only the other condition requires a warning/critical state and an Alert is triggered.
   
   This can be done easily by adjusting the condition you don’t want to use to such a level (like 80% for instance when you don’t want to use the percentage condition) so it’s already in a warning/critical condition. Now only the other condition (amount of free MBs) must met in order to trigger an Alert.
   
   
2. Change the Alert on State setting for this Monitor so ONLY an Alert is created when a Critical condition is met. This way an Alert won’t be missed in the Console, nor as a Notification nor by the Connector. 
   
   Now you could argue that a Critical condition won’t give you enough time to solve the issue before the server stops functioning.
   
   HOWEVER, this monitor can be modified on many other parameters as well in order to trigger a Critical Alert at an earlier stage, when the logical disk isn’t too full (Error Mbytes Threshold for Non-System Drives and Error Mbytes Threshold for System Drives).
   
   
   By bumping up those thresholds you’ll have enough time to remedy it when a Critical Alert comes in .

As you can see, this MP offers many possibilities for monitoring logical disk free space on your Windows Servers. Combined with all the parameters which can be modified this kind of monitoring can meet the requirements of your organization as well.