lemkeant

Okay, thank you Christopher, I deleted the System Volume Information folder from the Drivepool drive and the warning has gone away.
(I could not delete from the GUI, even after changing permissions, but del /f worked from command prompt)

It means the pool drive.  And yeah... how Windows handles disk/partition/volume stuff is confusing... at best. 
For this ... take ownership of the folder, change it's permissions, and delete it (on the pool). 
Then resolve the issue.  It should fix the issue, and shouldn't come back.