When a workstation cannot access the redundancy group of disks, it is typically indicative of a failure within the disk array that is designed to protect against data loss by distributing data across multiple disks. This setup commonly known as Redundant Array of Independent Disks, relies on all disks functioning correctly to maintain data integrity. A failure can lead to warnings or errors upon boot-up as the system cannot access or synchronize the data as configured. The other options are less likely to be the cause of disk redundancy group error messages as they pertain to separate hardware components unrelated to disk arrays.