If a VSAN node of more three nodes enters maintenance mode, is it not considered a fault-tolerant node?

[Neo Chen]

Hi All,

If a VSAN node of more three nodes enters maintenance mode, is it not considered a fault-tolerant node?

And there are two nodes can enters maintenance mode at the same times  without any issues.

[Geogee]

If you have 4 ESXi hosts, then you are able to put up to 2 hosts into maintenance mode without downtime of VMs. But placing host into maintenance mode makes him unavailable for sync of vSAN!! This is why vSAN best practice is to place only one host in the cluster into maintenance mode at one time.

If you have totaly only 3 hosts, then you can put into maintenace mode only 1 host at time.

[Neo Chen]

Hi @Geogee,

I want to know if putting a node into maintenance mode would represent a failure? 

If there are 4 nodes , I put a node into maintenance mode, can the cluster could be failed a node ?

[Geogee]

If you have 4 nodes and one is place into maintenance mode with "Migrate all data", then the cluster could survive unplanned failure of one other node. without data loss.

If you specify "Ensure availability" then there could be one other failure of the node, but data will be available after you recover the node from the maintenance mode. When you place node into maintenance mode, vSAN creates new "delta" components where stores writes made to components, which are missing due to maintenance mode node. This delta needs to be merged with the maintenance mode components before the objects are available again.