Found in the documentation : Volume Alarms - MapR 5.0 Documentation - doc.mapr.com
Meaning : This is a potentially very serious alarm that may indicate data loss. Some of the data on the volume cannot be located. This alarm indicates that enough nodes have failed to bring the replication factor of part or all of the volume to zero. For example, if the volume is stored on a single node and has a replication factor of one, the Data Unavailable alarm will be raised if that volume fails or is taken out of service unexpectedly. If a volume is replicated properly (and therefore is stored on multiple nodes) then the Data Unavailable alarm can indicate that a significant number of nodes is down.
Resolution : Investigate any nodes that have failed or are out of service.You can see which nodes have failed by looking at the Cluster Node Heatmap pane of the Dashboard.Check the cluster(s) for any snapshots or mirrors that can be used to re-create the volume. You can see snapshots and mirrors in the MapR-FS view.
Resolution : Investigate any nodes that have failed or are out of service.
Please check https://community.mapr.com/thread/21867-getvolumeace-rpc-failed-on-volume-in-mcs and see if the solution works for you.
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