Enabling the onboard cache on a RAID adapter card signi cantly enhances performance - especially in RAID 5 and RAID 6 scenarios - by accommodating both read caching and write caching of data. But data stored in the cache for write caching can be lost if the cache is not protected against a power or system failure.
Lithium-ion (Li-ion) battery backup units (BBUs) are traditionally employed to protect cached data on RAID adapters. Once installed, a new BBU will take several hours to reach a full charge. During the charge cycle, write cache is unprotected (i.e. turned o ), which adversly a ects the RAID adapter's performance. A typical BBU requires routine capacity testing and performs sub-optimally during those test periods. Lastly, a fully-charged BBU can only preserve data for a maximum of 72 hours during a power loss before the battery power depletes.