Microsoft released a KB article containing a fix for one of the following cases:
In System Center Operations Manager 2007 R2 environments you may see the following:
- The Data warehouse size grows, and upon investigation you discover that partitions are not being dropped/optimized even though grooming jobs are showing as running successfully.
- Report results do not match the resource availability and do not match the visible data in the Operations Manager console.
Keep in mind that the script to fix these items requires first that SCOM 2007 R2 with CU7 is installed a minimum version.
The KB article can be found here:
http://support.microsoft.com/kb/2872075