The disk usage metric shows the percentage of space used on the data partition of a node. Cadence nodes only use disk for temporary storage so there should rarely be an issue with disks filling up on Cadence nodes.
Instaclustr Support monitors disk usage for all managed clusters and will work with you to resolve the issue if your cluster is exceeding recommended levels of disk usage.
If your cluster is simply filling up with data then it can be easily scaled out by adding additional nodes. To do this, use the add node feature on our console or contact Instaclustr Support for assistance.