You can see the list by clicking a vCenter Server instance in the left column of the vSphere Client, then select Configure > Alarm Definitions and apply a “vsan” filter to the Alarm Name list. There are many vCenter Server alarms for vSAN. A proactive rebalance is commonly needed after adding capacity to a cluster and when maintenance mode with full data migration is used. A proactive rebalance can be stopped at any time, if needed. An administrator must initiate a proactive rebalance either from the vSAN Health UI or by command line. Note that a proactive rebalance is not started automatically. If the maximum variance between two capacity drives is more than 30%, the vSAN disk balance health check is yellow and the option to start a proactive rebalance is presented. The purpose is to promote a fairly even balance of resource utilization across the cluster. VSAN Health also produces a notification if the difference in capacity usage between two or more of the capacity drives is greater than 30%. More details on this can be found in the Adaptive Resync Tech Note. vSAN’s Adaptive Resync feature monitors and dynamically adjusts resource utilizations to avoid resync traffic contention with virtual machine traffic. If you are concerned that the traffic generated by rebalancing might impact virtual machine traffic, no worries. This rebalancing operation attempts to migrate data from drives that have usage above 80% to less-utilized vSAN capacity drives in the vSAN cluster. VSAN features a reactive rebalance mechanism that automatically starts when a physical drive crosses the 80% utilized mark. It is easy to see the recommendation here: It is best to keep the utilization of all capacity drives below 80%. Utilization above 95% results in a red alert. If a drive’s capacity usage is between 80% and 95%, a yellow warning is displayed. The Disk Capacity health check in the vSAN Health UI shows a green check as long as all of the capacity drives are less than 80% utilized. vSAN HealthĪs mentioned in the previous article, vSAN Health monitors the capacity of the physical drives that are used for vSAN capacity (not vSAN cache drives). We will discuss the alarms and notifications in vSAN Health and vCenter Server that can be used to keep an eye on vSAN datastore capacity usage. This article picks up where Part 1 of this series left off.
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