Dell PowerVault MD3000i Hardware Owner's Manual - Page 23
Removing and Installing a RAID Controller Module Backup Battery Unit - raid battery
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Battery Backup Unit Each RAID controller contains a three-cell lithium-ion battery backup unit (BBU) that powers the controller's cache memory and preserves the cache contents in the event of a power outage of up to 72 hours. The RAID controller firmware performs a test of the BBU at startup and will illuminate the battery fault LED if the battery is not operating within specified ranges, or if the battery is missing. The battery begins recharging automatically if the test determines that it is necessary. For a description of the battery fault LED, see Table 1-4. For information on removing and installing the BBU, see "Removing and Installing a RAID Controller Module Backup Battery Unit" on page 62. 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 reenabled. The RAID controller module logs the age of the battery and issues a replacement reminder message approximately six weeks before expiration. After replacing the battery, you must use MD Storage Manager to reset the battery age. RAID Enclosure Thermal Shutdown Enclosure management provides a feature that automatically shuts down the enclosure when the temperature within the storage enclosure exceeds a safe threshold. Thermal shutdown protects the data on the physical disks from corruption in the event of cooling system failure. Because the battery backup unit protects against cache data loss for up to 72 hours, all data in the cache is saved. It is not necessary to shut down any expansion enclosures attached to the storage enclosure. Temperature threshold values are used to determine the temperature at which shutdown occurs. These thresholds are default settings and cannot be changed. If the temperature sensors on the backplane detect a temperature exceeding the Nominal Failure Threshold, a critical event is set. If the Maximum Failure Threshold is reached, shutdown of the enclosure power supplies occurs within 3 minutes. A third threshold, the Shutdown Threshold, shuts down the enclosure power supplies within 5 seconds after it is reached. About Your System 23