The caching SSDs contain two write logs with a size of 12GB each. At all times 1 write log is active and 1 write log is passive. Writes are always performed to the active write log at the SSD cache layer and when full it gets de-staged to the HDD/SSD capacity layer.
During destaging the data is optimized by deduplication and compression before writing it to the persistent HDD/SSD layer.
Cisco, HyperFlex [HCI]/4.0, x86
Persistent Write Buffer, Reads/Writes, Data Availability