Open the shell, (either from the GUI-or with ssh) and type
zpool scrub poolname (where poolname is the name of your pool - repeat for each pool if you have multiple pools-you don't have to wait for the first scrub to finish, you can do more than one at a time).You can check the results with
zpool status (will list status for all pools, and if you don't remember your pool names this is a good way to get them.) If there are errors you will get a message, otherwise it will indicate that the scrub completed without error.I think there is a way to do it though the GUI as well, but the shell is so easy, that's the way I've always done one shot scrubs.
Hope that helps.
