You can monitor the status of virtual machine objects that are being resynchronized in the Virtual SAN cluster.

When a hardware device, host, or network fails, or if a host is placed into maintenance mode, Virtual SAN initiates resynchronization in the Virtual SAN cluster. However, Virtual SAN might briefly wait for the failed components to come back online before initiating resynchronization tasks.

The following events trigger resynchronization in the cluster:
  • Editing a virtual machine (VM) storage policy. When you change VM storage policy settings, Virtual SAN might initiate object recreation and subsequent resynchronization of the objects.

    Certain policy changes might cause Virtual SAN to create another version of an object and synchronize it with the previous version. When the synchronization is complete, the original object is discarded.

    Virtual SAN ensures that VMs continue to run and are not interrupted by this process. This process might require additional temporary capacity.

  • Restarting a host after a failure.
  • Recovering hosts from a permanent or long-term failure. If a host is unavailable for more than 60 minutes (by default), Virtual SAN creates copies of data to recover the full policy compliance.
  • Evacuating data by using the Full data migration mode before you place a host in maintenance mode.
  • Exceeding the utilization threshold of a capacity device. Resynchronization is triggered when capacity device utilization in the Virtual SAN cluster approaches or exceeds the threshold level of 80 percent.

If a VM is not responding due to latency caused by resynchronization, you can throttle the IOPS used for resynchronization.