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Question

You have a failover cluster named Cluster1 that has the following configurations:
✑ Number of nodes: 6
✑ Quorum: Dynamic quorum
✑ Witness: File share, Dynamic witness
What is the maximum number of nodes that can fail simultaneously while maintaining quorum?

Proposed answer
  • A. 1
  • B. 2
  • C. 3
  • D. 4
  • E. 5
Suggested answer
  • C. 3
Comments
wouter0121

Highly Voted 1 year, 2 months ago 

E is not correct it says simultaneously so at the same time. Its correct a vote gets removed when a host crashes but if it all happends at the same time the cluster will be gone. Answer is 3

upvoted 9 times 

starseed

Most Recent 3 months ago 

answer is 3

upvoted 1 times 

smorar

6 months, 1 week ago 

Selected Answer: C

3 is correct.

upvoted 3 times 

bpaccount

6 months, 2 weeks ago 

Selected Answer: C

3 is correct.

upvoted 2 times 

Kuikz

7 months ago 

Selected Answer: C

i agree with Deidros

upvoted 1 times 

Sc00by77

1 year ago 

Selected Answer: C

Dynamic Quorum specifically states that it does not work in simultaneous shutdowns which is called out in the question. The answer is 3.

upvoted 3 times 

tomasek88

1 year, 4 months ago 

Selected Answer: E

E --> is correct answer --> because dynamic quorum

upvoted 2 times 

klwood2000

1 year, 2 months ago 

Dynamic Quorum specifically states that it does not work in simultaneous shutdowns which is called out in the question. The answer is 3.

upvoted 2 times 

[Removed]

1 year, 4 months ago 

https://www.mssqltips.com/sqlservertip/4434/dynamic-quorum-for-windows-server-2012-r2-cluster-to-support-sql-server-alwayson/

upvoted 1 times 

[Removed]

1 year, 4 months ago 

Check this out, very good... Answer is E

upvoted 1 times 

ala76nl

1 year, 5 months ago 

Answer is E https://www.starwindsoftware.com/blog/understand-failover-cluster-quorum

upvoted 1 times 

Deidros

1 year, 2 months ago 

Excellent link but I think you missed a key part of the explanation : "So for the stretched cluster scenario, if you lose a room, the failure is simultaneous and the dynamic quorum has not the time to recalculate the majority of votes." The question does state that the failures are simultaneous. So the Dynamic Quorum doesn't compute the new quorum required and we can't go down to the "Last-man standing" situation. If all the fails are sequential, it seems to be indeed possible to get down to one node with the configuration showed in the question. But again, with simultaneous fails, we need to have no more than 3 nodes that fail so that we keep the quorum of 4 thanks to our initial 6 nodes + 1 active dynamic witness due to the starting even number of nodes. That will leaves us with 3+1 votes and the cluster runs. If 4 nodes crashes SIMULTANEOUSLY, we are left with 2+1 votes and the cluster shuts down. Again, that is my understanding because Microsoft documentation isn't clear in the 4 nodes example about that fact that the failures are sequentials.

upvoted 1 times 

phi3nix

1 year, 6 months ago 

I asked MS as I have access to support answer is C. "In our case, if all 6 nodes are healthy, we have 7 votes in cluster, the cluster can accept losing 3 votes(nodes) at most simultaneously to remain the cluster online, as 4 votes(3 nodes+dynamic witness) still constitute the majority of cluster If we have a node down, then 5 nodes healthy in cluster, the witness doesn't have vote, 5 votes now, it's acceptable that 2 nodes failed simultaneously."

upvoted 4 times 

arnitjoe

1 year, 6 months ago 

https://learn.microsoft.com/en-us/azure-stack/hci/concepts/quorum "Dynamic quorum enables the ability to assign a vote to a node dynamically to avoid losing the majority of votes and to allow the cluster to run with one node (known as last-man standing). Let's take a four-node cluster as an example. Assume that quorum requires 3 votes. In this case, the cluster would have gone down if you lost two nodes. However, dynamic quorum prevents this from happening. The total number of votes required for quorum is now determined based on the number of nodes available. So, with dynamic quorum, the cluster will stay up even if you lose three nodes......" So, the answer is E since in this question it's a six-node cluster so five nodes can fail.

upvoted 2 times 

phi3nix

1 year, 6 months ago 

No, my friend. The answer is C. We always need the majority of the votes.

upvoted 1 times 

syu31svc

1 year, 7 months ago 

Selected Answer: C

https://learn.microsoft.com/en-us/azure-stack/hci/concepts/quorum If you have an even number of nodes plus witness, the witness votes, so the total is odd Up to 3 can fail leaving 3 nodes and 1 witness for the vote Answer is C

upvoted 2 times 

wyvern8888

1 year, 7 months ago 

With dynamic quorum and a file share witness, the maximum number of nodes that can fail simultaneously while maintaining quorum in a failover cluster is calculated as follows: Maximum number of nodes that can fail = ((Total number of nodes + 1) / 2) - (Number of witness votes) In this case, there are 6 nodes and a dynamic file share witness. Since the witness is also dynamic, it will be given a vote only when needed. The default witness vote is 1. Therefore, the maximum number of nodes that can fail while maintaining quorum is: ((6+1)/2) - 1 = 2 This means that up to two nodes can fail simultaneously while maintaining quorum in Cluster1. Therefore, the answer is option B - 2.

upvoted 1 times 

SJHCI

1 year, 8 months ago 

Selected Answer: C

C is correct

upvoted 2 times 

azubi

1 year, 8 months ago 

Selected Answer: E

https://learn.microsoft.com/en-us/azure-stack/hci/concepts/quorum#how-cluster-quorum-works The total number of votes required for quorum is now determined based on the number of nodes available. So still one node and witness online.

upvoted 4 times 

cris66

1 year, 10 months ago 

the cluster requires more than half of the total votes to achieve quorum. 6 nodes + 1 witness. 4 required. 3 disks + 1 witness. 3 of 6 disks can fail.

upvoted 3 times 

Robrol

1 year, 10 months ago 

Selected Answer C - is correct. https://learn.microsoft.com/en-us/azure-stack/hci/concepts/quorum#how-cluster-quorum-works "When nodes fail, or when some subset of nodes loses contact with another subset, surviving nodes need to verify that they constitute the majority of the cluster to remain online. If they can't verify that, they'll go offline." We have a dynamic quorum with dynamic witness with 6 nodes. The majority of the cluster means, that we need 4 votes, which can be done with 3 nodes up plus a witness. So if 3 nodes will fail simultaneously, the system will still maintain the quorum.

upvoted 2 times 

nefaxto

1 year, 10 months ago 

Selected Answer: C

I think yes even the explanation of MS make me a little confused https://learn.microsoft.com/en-us/azure-stack/hci/concepts/quorum#four-nodes-with-a-witness

upvoted 2 times 

xxxxx85xx

2 years, 8 months ago 

Correct Answer

upvoted 4 times