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Cluster Quorum - Node and Disk Expand / Collapse
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Posted Wednesday, October 31, 2012 1:17 AM
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Hi Guys

Please help me understand something the Cluster Quorum and specifically Node and Disk Majority

I understand that if you have an even amount on nodes on your cluster, it's recommended to implement Node and Disk Majority. To avoid the split-brain effect and other undesirables.

My question is, if your disk that you have specified as your Quorum disk goes down, does it take the entire cluster down?

Thanks
Post #1379173
Posted Wednesday, October 31, 2012 2:47 AM


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SQLSACT (10/31/2012)
Hi Guys

Please help me understand something the Cluster Quorum and specifically Node and Disk Majority

I understand that if you have an even amount on nodes on your cluster, it's recommended to implement Node and Disk Majority. To avoid the split-brain effect and other undesirables.

My question is, if your disk that you have specified as your Quorum disk goes down, does it take the entire cluster down?

Thanks

Not necessarily, it depends on what other votes are around at the time of failure. More on the new quorum models can be found at this link.

Also, the link above states

Technet online
Can sustain failures of half the nodes (rounding up) if the disk witness remains online. For example, a six node cluster in which the disk witness is online could sustain three node failures.

Can sustain failures of half the nodes (rounding up) minus one if the disk witness goes offline or fails. For example, a six node cluster with a failed disk witness could sustain two (3-1=2) node failures.


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Post #1379202
Posted Wednesday, October 31, 2012 3:51 AM
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Perry Whittle (10/31/2012)
SQLSACT (10/31/2012)
Hi Guys

Please help me understand something the Cluster Quorum and specifically Node and Disk Majority

I understand that if you have an even amount on nodes on your cluster, it's recommended to implement Node and Disk Majority. To avoid the split-brain effect and other undesirables.

My question is, if your disk that you have specified as your Quorum disk goes down, does it take the entire cluster down?

Thanks

Not necessarily, it depends on what other votes are around at the time of failure. More on the new quorum models can be found at this link.

Also, the link above states

Technet online
Can sustain failures of half the nodes (rounding up) if the disk witness remains online. For example, a six node cluster in which the disk witness is online could sustain three node failures.

Can sustain failures of half the nodes (rounding up) minus one if the disk witness goes offline or fails. For example, a six node cluster with a failed disk witness could sustain two (3-1=2) node failures.


Thanks

In my case, I have a 2 node 2008 cluster with Node and Disk Majority

I took down the Quorum drive and the entire cluster went down

Normal?
Post #1379219
Posted Wednesday, October 31, 2012 4:09 AM


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SQLSACT (10/31/2012)
Perry Whittle (10/31/2012)
SQLSACT (10/31/2012)
Hi Guys

Please help me understand something the Cluster Quorum and specifically Node and Disk Majority

I understand that if you have an even amount on nodes on your cluster, it's recommended to implement Node and Disk Majority. To avoid the split-brain effect and other undesirables.

My question is, if your disk that you have specified as your Quorum disk goes down, does it take the entire cluster down?

Thanks

Not necessarily, it depends on what other votes are around at the time of failure. More on the new quorum models can be found at this link.

Also, the link above states

Technet online
Can sustain failures of half the nodes (rounding up) if the disk witness remains online. For example, a six node cluster in which the disk witness is online could sustain three node failures.

Can sustain failures of half the nodes (rounding up) minus one if the disk witness goes offline or fails. For example, a six node cluster with a failed disk witness could sustain two (3-1=2) node failures.


Thanks

In my case, I have a 2 node 2008 cluster with Node and Disk Majority

I took down the Quorum drive and the entire cluster went down

Normal?

No, as 2 out of 3 votes would have still been available.

Having said that, in your config, removal of the disk witness would not sustain any further node failures.

Re run the cluster validation report and check for errors, also check the event and cluster logs for issues too


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"Ya can't make an omelette without breaking just a few eggs"
Post #1379222
Posted Wednesday, October 31, 2012 4:35 AM
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Perry Whittle (10/31/2012)
SQLSACT (10/31/2012)
Perry Whittle (10/31/2012)
SQLSACT (10/31/2012)
Hi Guys

Please help me understand something the Cluster Quorum and specifically Node and Disk Majority

I understand that if you have an even amount on nodes on your cluster, it's recommended to implement Node and Disk Majority. To avoid the split-brain effect and other undesirables.

My question is, if your disk that you have specified as your Quorum disk goes down, does it take the entire cluster down?

Thanks

Not necessarily, it depends on what other votes are around at the time of failure. More on the new quorum models can be found at this link.

Also, the link above states

Technet online
Can sustain failures of half the nodes (rounding up) if the disk witness remains online. For example, a six node cluster in which the disk witness is online could sustain three node failures.

Can sustain failures of half the nodes (rounding up) minus one if the disk witness goes offline or fails. For example, a six node cluster with a failed disk witness could sustain two (3-1=2) node failures.




In my case, I have a 2 node 2008 cluster with Node and Disk Majority

I took down the Quorum drive and the entire cluster went down

Normal?

No, as 2 out of 3 votes would have still been available.

Having said that, in your config, removal of the disk witness would not sustain any further node failures.

Re run the cluster validation report and check for errors, also check the event and cluster logs for issues too



Thanks

What I forgot to mention is that the Cluster went down and then came back up again after a few seconds. The Quorum drive also came up

Thanks
Post #1379234
Posted Wednesday, October 31, 2012 4:52 AM


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check your event logs for more info, there'll be some errors there that will be relative.

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Post #1379239
Posted Wednesday, October 31, 2012 4:57 AM
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Perry Whittle (10/31/2012)
check your event logs for more info, there'll be some errors there that will be relative.


Thanks for your help
Post #1379242
Posted Wednesday, October 31, 2012 8:37 AM


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you're welcome

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Post #1379359
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