Wednesday, June 6, 2018

Cache Vault versus Disk controller Batteries



  • Older generations of RAID controllers used lithium-ion based battery backup units to keep the data resonate in the cache memory until power could be restored. 
  • Data was only available for up to 72 hours. Over the life of a controller, the battery will need to be replaced numerous times, as it is only good for about 1 ½ years, which increases cost of ownership. 
  • Unlike supercapacitors, batteries cannot sit on the shelf for a long period of time without requiring re-charging, making inventory management costly. 
  • Further, shipping and disposing lithium-ion batteries requires special considerations and fees. RAID controller cards temporarily cache data from the host system until it is successfully written to the storage media.
  • While cached, data can be lost if system power fails, jeopardising the data's permanent integrity. RAID caching is cost-effective way to improve I/O peformance by writing data to a controller's cache before it is written to disk.
  • However, in the event of a power of server failure, the writes in cache may be lost.
  • CacheVault flash cache protection modules and battery backup units (BBUs) protect the integrity of cached data by storing cached data in non-volatile flash cache storage or by providing battery power to the controller.
  • CacheVault technology prevents data loss by powering critical components of the card long enough to automatically transfer the cached data to NAND flash. 
  • Once power returns, the data is restored to the cache and normal operation resumes. By using a super-capacitor instead of Lithium-ION batteries, CacheVault technology virtually eliminates hardware maintenance costs associated with batteries, lowers total cost of ownership over the life of the controller card and provide more environmentally friendly cache protection, all while maintaining optimal RAID performance.
  • Oracle Exadata Database Machine X6 has no batteries. Newer machines have CVPM02 (Cache Vault), which is a super cap and not a battery.





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