Owner manual

RAID Controller Module—Additional Features

Battery Backup Unit

Each RAID controller contains a two-cell Lithium ion nanopolymer battery backup unit (BBU). It provides

power to the RAID controller module in the event of a power outage. For information on removing and

installing the BBU, see RAID Controller Module Backup Battery Unit .

NOTE: For virtual disks, the RAID controller firmware changes the data cache setting based on the

state of the battery. If the battery is missing or does not have sufficient charge, the controller flushes

the cache and sets the write cache attribute to Write Through for all virtual disks. When the battery

is replaced, Write Back is re-enabled.

Storage Array Thermal Shutdown

The system automatically shuts down when system temperature exceeds the safe threshold. The battery

backup unit protects against data loss by providing power to offload cache to non-volatile memory in the

event of power loss. It is not necessary to shut down any MD1200 Series expansion enclosures attached

to the storage array when thermal shutdown occurs.

Temperature threshold values determine the temperature at which shutdown occurs. These thresholds

cannot be changed.

Table 1. Shutdown Threshold Type

Threshold Temperature Exceeding Event Description

Nominal failure threshold A critical event is set.

Maximum failure threshold Shutdown of the system power supplies occurs

within 3 minutes.

Shutdown threshold Shutdown of the system power supplies occurs

within 5 seconds.

System Password Reset

The storage array password can be reset if it is forgotten. To reset the password, push and hold down the

password reset switch for at least 5 seconds. The password is deleted.

The RAID controller module allows you to change the password.

NOTE: The reset switch can be accessed by using a small object such as the tip of a pen.

Cache Functions and Features

Cache Mirroring

Cache mirroring function copies accepted host-write data from the primary controller to the partner

controller. This action ensures that host-write data is safely mirrored to the partner controller before

successful completion status is returned to the host. If a controller fails, the surviving controller safely

retains all mirrored data. Cache mirroring is enabled by default.