columnstore does not allow mysql data dir to be overridden

if you overrider the datadir variable in my.cnf under columnstore, then mariadb server will be happy with that and use the db tree there. However there are checks in the columnstore code that are hardwired to check for the pid file only under the install-dir / mysql db directory.

A workaround is softlink the db directory to the required location but it would be less error prone to correctly support datadir overriding the location for innodb data files etc.