Place a member of vSAN Cluster in Maintenance Mode

In the last blog, we discussed about the different options which are available when working with Maintenance mode in vSAN Cluster. In this blog, lets discuss about each of them in detail.

Before you enter any host into maintenance mode, verify that your environment has the capabilities required for the option you select.

Procedure -

1. Right-click the host and select Maintenance Mode > Enter Maintenance Mode.

2. Select a data evacuation mode and click OK. As previously discussed, there are 3 options available.

a. Ensure accessibility

This is the default option. When you power off or remove the host from the cluster, vSAN ensures that all accessible virtual machines on this host remain accessible. Select this option if you want to take the host out of the cluster temporarily, for example, to install upgrades, and plan to have the host back in the cluster. This option is not appropriate if you want to remove the host from the cluster permanently. Typically, only partial data evacuation is required. However, the virtual machine might no longer be fully compliant to a VM storage policy during evacuation. That means, it might not have access to all its replicas. If a failure occurs while the host is in maintenance mode and the Failures to tolerate is set to 1, you might experience data loss in the cluster. This is the only evacuation mode available if you are working with a three-host cluster or a vSAN cluster configured with three fault domains.

b. Full data migration

vSAN evacuates all data to other hosts in the cluster and maintains the current object compliance state. Select this option if you plan to migrate the host permanently. When evacuating data from the last host in the cluster, make sure that you migrate the virtual machines to another datastore and then place the host in maintenance mode. This evacuation mode results in the largest amount of data transfer and consumes the most time and resources. All the components on the local storage of the selected host are migrated elsewhere in the cluster. When the host enters maintenance mode, all virtual machines have access to their storage components and are still compliant with their assigned storage policies. If a virtual machine object that has data on the host is not accessible and is not fully evacuated, the host cannot enter maintenance mode.

c. No data migration

vSAN does not evacuate any data from this host. If you power off or remove the host from the cluster, some virtual machines might become inaccessible.

You can also place a host in the maintenance mode from command line by using the ESXCLI Commands. Before placing a host in this mode, ensure that you powered off the VMs that run on the host.

To enter maintenance mode, run the following command on the host:

esxcli system maintenanceMode set --enable 1

To verify the status of the host, run the following command:

esxcli system maintenanceMode get

To exit maintenance mode, run the following command:

esxcli system maintenanceMode set --enable 0

I hope you find this post useful.

Thank you for reading!

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