minimum DRS cluster size

[xbradshr]

What is the minimum recommended DRS cluster Size. Is it the case that 2 would be a technical minimum? But is there a minimum size that is more efficient?

[Gkeerthy]

at least you need to have 3 so even if one host fails also the entire load will be distributed to 2 hosts, for a cluster minimum 2 is enough, but if one host fails you will be in a single point failure. So i recommend at least 3 host for a cluster.

[a_p_ · Accepted solution]

Is it the case that 2 would be a technical minimum?

Yes, you can start using DRS with two nodes.

But is there a minimum size that is more efficient?

Although it's certainly desirable to have more hosts, DRS actually works the same way with two hosts as it works with 32 hosts. The responsibility of DRS is not to load balance a cluster, but to migrate workloads if required.

André

[UmeshAhuja]

Hi,

The below link will highlight you more clarification on your query.

http://www.yellow-bricks.com/2009/12/30/limit-your-cluster-size-to-8/

http://www.yellow-bricks.com/2010/11/29/re-maximum-hosts-per-cluster-scott-drummonds/

http://vpivot.com/?p=702

[Nuwanalwis]

DRS Cluster is no othere than a traditional cluster system. So like any other cluster topology minimum is N+1. (Now its seems too technical but its easy to understand)

"N" is the number of servers need to be protected or load share. So if you have 1 ESX server and you need to implement DRS or HA you need minimum of

1 ESX Server  + 1= 2 ESX server.

Hope above made you clear. And thats clustring basics.

So the answer to your question is its how cluster designed and not a technical limitation of vmware.

So whats wrong with 2 Node load balancing?

There is nothing wrong, Your DRS works fine and no issues at all and its technically vailed. The only issue you will face is that your DRS Cluster do not have much resource options to play with. so the optimization will not be visible because its load been shared back and forth between 2 ESX servers.

Think about a situation that both nodes of the DRS cluster equally busy, so there is nothing much DRS can do becaus its been reached the limit of the cluster.

But if you had 3 nodes cluster it adds more resources to the DRS cluster to balance the load across ESX.

Plus This also give the time for administrators to plan ahead and add more resource to their clusters as required.

Personally i think more advantage comes from 3 Node cluster when talking about HA protection. (This is my personal idea)