ArmorCache Technology
In an emergency power off (EPO) scenario, a drive has very limited time to perform operations to ensure a proper shutdown. Upon recognition of power failure, a drive must first retract the heads from the media and then perform various “housekeeping” tasks to commit drive metadata in volatile DRAM to a non-volatile memory (NVM).
While enterprise solid-state drives (SSDs) require large banks of capacitors to ensure enough remaining power to properly shut down, HDDs have a built-in energy source that they can use to provide this power: spinning disks.
Upon EPO, the HDD uses the rotational energy of the spinning disks to generate electricity. Akin to that created by a turbine generator, or by regenerative braking on an electrical vehicle, this energy gives the HDD time to perform its necessary housekeeping and write critical data to NVM. To date, however, the amount and speed of NVM used has been insufficient to write a significant amount of cached user data upon EPO. OptiNAND adds a high-capacity and high-speed NVM device to the HDD. With the addition of OptiNAND, the capacity and speed of NVM is now sufficient to write all cached user data in DRAM to NVM.
Upon EPO, the HDD can flush the entire DRAM cache to the onboard iNAND® device. Crucially, it is able to do this in both WCE and WCD modes. This guarantees in WCE mode that any cached data wille be successfully written on EPO, and no user data will be lost. This also provides significantly larger caching capability in WCD mode, providing full performance while still guaranteeing all writes will be committed upon EPO.
