1- Open Operations Manager Console.
2- Navigate to Authoring.
3- Under monitors scroll down till reach Windows Server 2008 Logical Disk >> Entity Health >> Availability >> Windows Server 2008 Logical Disk – Free Space (%) Low.
4- Right click on Windows Server 2008 Logical Disk – Free Space (%) Low >> Overrides >> Override the Monitor >> For All objects of class: Windows Server 2008 Logical Disk.
5- Reconfigure values as below then click OK.
Feel free to reconfigure the threshold as your
6- Below Alert you will got if the free space reached configured threshold