Dell MD3620I RAID Controller Module-Additional Features, Battery Backup Unit, Event Description

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" on page 222.

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 the system temperature exceeds the safe threshold. The battery backup unit protects against data loss by providing power to offload 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 3-1. Shutdown Threshold Type

Threshold Temperature Exceeding	Event Description
Nominal failure threshold	A critical event is set
Maximum failure threshold	The system power supplies shut down within 3
	minutes
Shutdown threshold	The system power supplies shut down within 5
	seconds

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Planning: RAID Controller Modules