The controller has detected a latent error in the backup Disk Configuration Block (DCB).

The 3ware RAID controller checks the backup DCB, even when the primary DCB is OK. If an error is found, the controller will attempt to correct the error by reading the primary copy. If the primary copy is valid, the backup DCB will be rewritten to rectify the errors.

LSI recommends verifying the unit. See Starting a Verify Manually.