I had a RAID5 volume in Centos7, the number of disks were 3 in the array. Now I am trying to grow the RAID5 volume with additional 1 disk but getting error while growing the RAID5 volume.Command: # mdadm --grow /dev/md0 --level=5 -n 4mdadm: Need to backup 3072K of critical section..  mdadm: Cannot start reshape for /dev/md0  unfreeze
Grow RAID5 array
centos;raid;software raid
It worked after updating the mdadm version to v3.3.4. Thanks to Frostschutz. 