How to Put a VSAN Host to Maintenance

How to Put a VSAN Host to Maintenance

Just use below blog post and it explain everything perfectly. 
 https://blogs.vmware.com/virtualblocks/2018/10/29/a-closer-look-at-emm/

Maintenance Mode Considerations for vSAN

Since each vSAN host in a cluster contributes to the cluster storage capacity, entering a host into maintenance mode takes on an additional set of tasks when compared to a traditional architecture.  For this reason, vSAN administrators are presented three host maintenance mode options:

• Full Data Migration – evacuate all of the components to other hosts in the cluster
• Ensure Accessibility – evacuate enough components to ensure that virtual machines can continue to run, but non-compliant with the respective storage policies
• No Data Migration – Don’t evacuate any components from this host

Full Data Migration 
This option moves all of the vSAN components from the host entering maintenance mode to other hosts in the vSAN cluster. This option is commonly used when a host will be offline for an extended period of time or permanently decommissioned.
Ensure accessibility 
vSAN will verify whether an object remains accessible even though one or more components will be absent due to the host entering maintenance mode. If the object will remain accessible, vSAN will not migrate the component(s). If the object would become inaccessible, vSAN will migrate the necessary number of components to other hosts ensuring that the object remains accessible. This option is the default and it is commonly used when the host will be offline for just a short amount of time, e.g., a host reboot. It minimizes the amount of data that is migrated while ensuring all objects remain accessible. However, the level of failure tolerance will likely be reduced for some objects until the host exits maintenance mode. vSAN’s object manager will wait 60 minutes (by default) before it tries to initiate any resynchronizations to regain the level of resilience originally assigned by the policy.
No data evacuation
Data is not migrated from the host as it enters maintenance mode regardless of what the  level of failures to tolerate dictates in policy. Technically, this option can also be used when the host will be offline for a short period of time, but since no data is migrated, virtual machines with no data redundancy (i.e. RAID-0) will be unavailable.  This option is commonly used when decommissioning a host and you don't want to wait for the full migration. Again, vSAN’s object manager will wait 60 minutes (by default) before it tries to initiate any resynchronizations to regain the level of resilience originally assigned by the policy.