Chapter 2
Components
19
writing incomplete data to disk, the image stored in the eMMC card is verified before committing to disk. The eMMC
plugs into a slot on the controller module baseplane. Given that the controller module is a sealed component, the eMMC
is not accessible.
NOTE In dual-controller configurations featuring a healthy partner controller, the cache is duplicated between the
controllers provided that volume cache is set to standard on all volumes in the pool owned by the failed controller.
Supercapacitor pack
To protect RAID controller cache in case of power failure, HPE MSA controller modules are equipped with supercapacitor
technology, which in conjunction with internal non-volatile memory, provides extended cache memory backup time.
The supercapacitor pack provides energy for backing up unwritten data in the write cache to the non-volatile memory
in the event of a power failure. Unwritten data in non-volatile memory is automatically committed to disk media when
power is restored. While the cache is being maintained by the supercapacitor, the Cache Status LED flashes at a rate of
1/10 second on and 9/10 second off.