If Cluster managed voting is Enabled do you still need quorum witness?

[AlteredAdmin]

Afternoon,

 

Fail over cluster if Cluster managed voting is Enabled do you still need quorum witness?

 

The reason i ask is because we set up a 3 node cluster but still get the "The cluster is not configured with a quorum witness. As a best practice, configure a quorum witness to help achieve the highest availability of the cluster." on validation even though Cluster managed voting: Enabled

 

if a witness is needed for 3 nodes how is that different from 2 nodes with a share witness?

This will be used for SQL.Thoughts?

This will be used for SQL.

[Steve21]

It's not "needed" as per the warning, it's just best reliability, with dynamic quorum management you can go down to a single node and still have a proper vote. Otherwise it'd automatically be split.

 

In basic terms (ok yes if you query it a lot this isn't entirely accurate), but you need 50% of hosts up without witness. So in a 3 node, you'd need 2 hosts (without witness). With witness you can need 1+1witness, as the 2/4 combo etc

 

Steve

[AlteredAdmin]

It's not "needed" as per the warning, it's just best reliability, with dynamic quorum management you can go down to a single node and still have a proper vote. Otherwise it'd automatically be split.

 

In basic terms (ok yes if you query it a lot this isn't entirely accurate), but you need 50% of hosts up without witness. So in a 3 node, you'd need 2 hosts (without witness). With witness you can need 1+1witness, as the 2/4 combo etc

 

Steve

So i keep thinking that a node votes in the same way that witness does. But starting to think that is not the case.

 

For example all nodes votes are special, but a witness's vote is extra special?

[HPlum78]

So here is the MS guide that gives the absolute detail on this rather than me writing it out:

https://docs.microsoft.com/en-us/azure-stack/hci/concepts/quorum

 

Note the statement:

Cluster quorum recommendations

If you have two nodes, a witness is required.

If you have three or four nodes, witness is strongly recommended.

 

Strongly recommended in a 3 node cluster further down the doc outlines what scenarios the various cluster configurations can operate under and the liklihood of the cluster being able to continue in those failure scenarios.

[Warwick_Tech]

Hijacking this thread!

 

Can the witness be a RaspberryPi? (Linux) as this is my plan...

[slugshead]

I'd still add it in as per best practise. 200-400GB partition on the SAN is perfectly adequate.

 

Presenting it as a cluster storage also means the owner node can switch and move around like your regular pools