1-BBU Cache Enable ModeWhen only a single battery backup unit is installed, the write cache operation mode canbe set using the management software (NEC Storage Manager). In this state, rememberthat if a fault occurs in the battery backup unit, the failed battery backup unit must bereplaced with a new one immediately to avoid data loss. Ask your service representativeto replace the battery backup unit. Note also that data retention time is reduced to halfthe normal time (i.e. when two BBUs are installed).OFF: The write cache is disabled in the single-BBU condition.ON: The write cache is enabled even in the single-BBU condition. (factory-set)Note: The single-BBU condition refers to the state in whichonly one battery backup unit is mounted to the disk array unit, or onlyone of the two battery backup units is available due to a failure.1-CNT Cache Enable ModeWhen only a single controller is installed, the write cache operation mode can be setusing the management software (NEC Storage Manager). However, it is recommendedto disable this mode to avoid any loss of data should a fault occurs in the controller.OFF: The write cache is disabled in the single-controller condition. (factory-set)ON: The write cache is enabled even in the single-controller condition.Note: The single-controller condition refers to the state inwhich only one controller is mounted to the disk array unit, or onlyone of the two controllers is available due to a failure.System Overview 1-21
