vSAN network maintenance

[mike-p]

I have a stretched cluster and need to change the connection between the locations. Theoretically i need to set all hosts of one location in maintenance mode. All vm's are distributed only with PFTT=1 , SFTT=0. Which impact would i expect if i disable HA or Admission Control instead of moving all vm's? I will get a vSAN alarm but the access to the objects is the same as maintenance mode with "ensure accessibility". The Advantage wold be that i can use the resources of all hosts.

[depping · Accepted solution]

But disabling HA and Admission Control doesn't prevent what is going to happen in this situation.

Your VMs are replicated between locations, and you have VMs in both preferred and the secondary. When the ISL goes down, the Preferred location will bind itself with the witness, the secondary will lose access to the witness. Which means that ALL virtual machines in the secondary instantly lose access to storage and will be marked inaccessible and killed by vSAN.

NORMALLY they would be restarted by HA in the preferred location, but in this case if you disable HA then nothing would happen.

I would highly recommend moving ALL the virtual machines to the preferred location before doing the maintenance.