Three years after the formation of the last significant branch, the mdadm 4.2.0 package is released, which includes a set of tools for managing software RAID arrays in Linux. Of the changes in the new version, it is noted that it is possible to build using GCC 9 and expand support for IMSM (Intel Matrix Storage Manager) RAID arrays, as well as the Partial Parity Log (PPL) functionality used in them, which allows you to save additional redundant data to reduce the likelihood of information corruption ( Write Hole) in case of desynchronization of disk contents. The new version also improves support for cluster RAID1/10 (Cluster MD), which allows you to deploy software RAID for all cluster nodes.
Source: opennet.ru