A physical link between the enclosure and expansion enclosure, and it transfers I/O.
A physical disk channel can have a status of either or . When Optimal, the RAID controller modules use the channel for transferring host I/O to the physical disks. When Degraded, the RAID controller modules use the physical disk channel when no other path is available or when I/Os have failed on all other paths.
Physical Disk channels can be set to Degraded by the RAID controller module if the channel has a recent history of
errors or manually by a system administrator.