Disk Array States

Array State Transitions
The movement between states is illustrated in the following diagram.

•  Good
   The array is online and it can be read and written. Both member  disk drives of the array are present. No data rebuilding is  outstanding. The array is fully protected against the loss of  one member.

•  Exposed State
   One member is missing from the array. The first write operation  causes the array to enter the degraded state.

   After an interval, if a hot spare is available, it replaces the  missing member and the array enters the rebuilding state.

•  Degraded State
   One member is missing and a write operation has been received  for the array. Read and write operations to the array are supported. If  a hot spare disk drive is available, after an interval, the hot spare  replaces the missing member and the array enters the rebuilding  state.

   The missing member is permanently excluded from the array.

•  Rebuilding State
   The array is online and it can be read and written. Both  members of the array are present but data is being rebuilt on one of the  members.

•  Offline State
   An array is in this state when one of the following conditions exists:
  •  Both members of the array are missing or have failed.
  •  One member of the array is missing when a failover occurs.
  •  The rebuilding of a replacement member is not complete when the remaining original member fails.

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