Explanation/Reference:
One possibly cause is Disk I/O contention on the data volume.
The root volume in Cluster-Mode is used to store and update various tables of the replicated database.
Crucial information regarding the locations of LIFs, volumes, aggregates, and different jobs required to run
in the cluster are stored in these tables. If a root aggregate has very busy data volumes, the disks in the
aggregate will experience higher latency. When a node is unable to update its copy of the replicated
database fast enough, it will consider itself unhealthy and stop serving all the data until it can catch up.
This is extremely disruptive and affects all the volumes on the node, even if the cause is related to the data
volumes stored on the root aggregate only.
Reference: Why is a warning displayed when attempting to create one or more data volumes in the root
aggregate in Data ONTAP Cluster-Mode?
https://kb.netapp.com/support/index?id=3013563&page=content&locale=en_US