Hello,
In answer to Kinkin's question - if you remove dg3, the data that was written to those drives will be moved automatically to the other disk-groups within the pool. In your example that would be dg1 and dg2.
Since this is virtual system, the volume is striped across the disk-groups within the pool. It is not a one to one relationship with a vdisk owning a volume as you would find with a linear system. With virutal there is no way to associate one virtual volume to a single disk-group.
In response to Evzar - if you have data that is no longer needed on a volume you can delete that data from the host. That way you will not move unneeded data if you remove a disk-group. The array has no way to determine a single file/database and allow you the ability to delete that file/database from the array. As mentioned before, you can delete the Pool if all the data on volumes associated with that Pool are no longer needed.
Cheers,
Shawn
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