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Huawei V2 and V3 Server RAID Controller Card User Guide 36

This document describes the appearances and features of the redundant array of independent disks (RAID) controller cards, how to configure properties for the RAID controller cards, and how to install drivers. The RAID controller cards include the LSI SAS2208, LSI SAS2308, LSI SAS3008, LSI SAS3108, LSI SoftRAID, PM8060, and PM8068.
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Power Failure Protection

Power Failure Protection

When there is a large number of write operations, the speed at which data is written to the high-speed cache is greater than the speed at which data is written to hard disks. Enabling the high-speed cache improves the write performance of the entire system. When the write pressure of the server decreases or the cache is about to full, data will be written to hard disks from the cache.

However, enabling the high-speed cache also increases data loss risks. If the system is powered off unexpectedly, data in the cache will be lost. A battery or supercapacitor can be configured for the RAID controller card to improve the read/write performance of the entire system and security of data in the cache. The battery or supercapacitor starts to supply power to the cache only when the voltage of the cache is lower than the preset value. Once the voltage of the cache increases to the specified value, the RAID controller card supplies power to the cache. In this way, when the server is powered off unexpectedly, the battery or supercapacitor supplies power to the cache to ensure data security. When the server is powered on, the RAID controller card supplies power to the cache to ensure proper working of the cache.

To ensure cache data security and proper data synchronization from the cache to hard drives, the LSI SAS2208 cache data is protected against power failures using any of the following:

  • Intelligent battery backup unit (iBBU)

    When a power failure occurs, the iBBU supplies power for the cache. When the power supply recovers, the controller card writes the data in the cache to hard drives. The iBBU, however, provides a limited backup time for 12, 24, 48, or 72 hours. If the power supply is not recovered within the limited period of time, data will be lost.

  • Supercapacitor

    When a power failure occurs, the supercapacitor supplies power to the cache and data is written to the NAND flash of the supercapacitor. The NAND flash is a non-volatile storage medium. Therefore, the supercapacitor can provide approximate permanent protection for cache data.

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Updated: 2019-11-01

Document ID: EDOC1000004186

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