there are several options how to decrease data load. You can find all of them in Setup - Administration - Advanced Setup - System Properties menu.
1) most "painful" tables store Raw Performance Data. By decreasing "Days to Retain Raw Performance Data" (by default 14 days) property you'll get a lot of free space
2) you can also decrease hourly rollups "Days to Retain Performance Data Hourly Rollups"
3) if you monitor VMware with Fibre Channels and you don't need such samples then setting collection.vmware.skip_storagepath_samples to true will definitely save significant amount of space too
4) minor, but still worth to mention, are months.to.keep.alerts and months.to.keep.trends attributes. If you don't need full 12 month history of alerts & trends then adjust those properties according to your needs.
Wait one day to get the changes applied. Database maintenance job is held daily at 3:00 AM.
If amount of free space isn't sufficient after those changes then I suggest that you contact SolarWinds Support, send them logs and they might offer additional solutions.
Let me know if it helped.