Possible reasons:
  unknownReason(2),
  disabledByOperator(3),
  interconnectOffline(4),
  disabledByPartner(5),
  takeoverFailed(6),
  mailboxIsInDegradedState(7),
  partnermailboxIsInUninitialisedState(8),
  mailboxVersionMismatch(9),
  nvramSizeMismatch(10),
  kernelVersionMismatch(11),
  partnerIsInBootingStage(12),
  diskshelfIsTooHot(13),
  partnerIsPerformingRevert(14),
  nodeIsPerformingRevert(15),
  sametimePartnerIsAlsoTryingToTakeUsOver(16),
  alreadyInTakenoverMode(17),
  nvramLogUnsynchronized(18),
  stateofBackupMailboxIsDoubtful(19).