Posted by ErmanArslansOracleBlog on Jun 01, 2020; 9:05am URL: http://erman-arslan-s-oracle-forum.124.s1.nabble.com/Adding-disks-to-diskgroup-ASM-RAC-tp8408p8410.html
This is a Core DBA question actually.. A RAC Admin related question.. But it is fine.
You can check this MOS note :
How To Add a New Disk(s) to An Existing Diskgroup on RAC Cluster or Standalone ASM Configuration (Best Practices). (Doc ID 557348.1)