21.0.0

**Table 1** Features and documents related to 21.0.0
Feature	Document	Description
Smart write cache	Smart Write Cache Feature Guide (CentOS 7.6) Smart Write Cache Feature Guide (openEuler 20.03) Smart Write Cache Release Notes	The smart write cache uses I/O passthrough, Bcache QoS policy control, write back policy control, and GC policy control to improve the bcache performance and the Ceph cluster performance ultimately.