i'm unable to understand why 4 nodes are recommended for maximum availability.
I understand for FTT=1, you need 3 nodes (2n+1).
But then design guide states, if ESXi host fails you cannot rebuild component.
Quoted
"The implications of this are that if a node fails, vSAN cannot rebuild components, nor can it provision new VMs that tolerate failures"
For example there are Node1, Node2 and Node3. For simplicity there is only one VM is running on it. By Design there are 2 replicas of the data and a witness, and these must all reside on different hosts. Assume, Node 3 is holding Witness, if Node 3 is down what will be impact? I believe VM will continue to run but then witness will not be rebuild right?
Suppose we go with Four node cluster and put Node-3 into maintenance will it move the witness to Node-4?
There is statement in "essential-virtual-san - second edition book " chapter -09. I unable to understand why 8 nodes and not 7 nodes. I'm sorry unless you have read the book only Author of the book can explain.
- Minimum of six hosts to support RAID-6.
- Additional host to allow for full recovery and re-protection (self-healing) after a failure, which means seven hosts minimum.
- Additional host to allow for recovery and re-protection during maintenance, which means eight hosts minimum.