Customers always asked me, why it is not possible to enter maintenance mode for a host using the GUI, instead of the CLI. Well, now we can… Starting with AOS6.5 (LTS) an administrator is able to enter maintenance mode of a host using the Prism web interface. (Not sure, this was introduced in a STS version of AOS. Maybe it was a feature in an earlier release of AOS STS.)
Using the host tab of the hardware, we can enter maintenance mode for a host. What are the steps that are performed by AOS before putting a host in maintenance?
vCenter credentials are needed!
When you leverage ESXi as hypervisor you should always enter credentials for vCenter Server. When using AHV as hypervisor, entering credentials is not necessary.
Entering Maintencance mode
Before a host can entering maintenance mode, user virtual machines have to be migrated to another host. Non-migratable VMs will shutdown. When all steps are successfully finished, the CVM will enter maintenance mode and shut down.
All steps look familiar, but is always nice to have them orchestrated.
The shutdown of a Controller VM has a few steps you should know about. VMs with RF1 defined will shut down, as Nutanix cannot guarantee the data with a powered off CVM. All other subtasks should be familiar.
Exiting Maintenance Mode
Maybe a no-brainer, but when entering maintenance mode, please do not forget to exit maintenance mode. When a host is exiting maintenance mode, first of all the CVM is started and the Nutanix cluster will eventually functioning normally. With this step you also have to provide credentials when leveraging ESXi as the hypervisor.
Final note
Just a late remark on exiting maintenance mode. When a host has entered maintenance mode in another way than this orchestrated procedure, AOS will not be able to exit maintenance mode. AOS is only capable of exiting maintenance mode, when AOS is entering maintenance mode for this host.
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