On this Tab is displayed important status information about your existing RAID5 volumes ( arrays ). The illustration above shows a normal, healthy array.
The illustration above shows an array that has had 1 disk fail and is degraded but still usable / accessable. This array can be fixed by replacing the failed drive with no loss of data.
Generally a RAID5 array can survive the failure of only 1 drive, if 2 drives fail, data contained on the array is most likely lost. It is sometimes possible to use data recovery software to retrieve data from an array that has lost 2 drives. Remember that RAID does not equal backup.
The illustration above shows an array that has just had a drive replaced and is in the process of rebuilding ( da5 @ 61% ). It is possible to mount the array and use it while it rebuilds, response will be about 20% slower than normal until the rebuild is complete.