russ79
Enthusiast
Enthusiast

one cluster or two?

in a nutshell my current enviornment:

  • 1 Intel Cluster of 5 hosts (core 2 and i7) for production, attached to production san

  • 1 Intel Cluster of 2 hosts (core 2) for development, attached to development san

  • 4 Standalone Intel hosts (core 2) some for production, some for development

  • 6 Standalone AMD hosts (older opteron) for development

I am beginning the process of upgrading to vSphere and I've made the suggestion of pooling all of our Intel boxes into 1 cluster on the production san. We have enough capacity to retire our AMD boxes. I could use resource pools and vlans to keep production and development VMs separated. I am looking for any thoughts and comments on this plan. I think this might be a good idea but i'm curious to know if anyone thinks otherwise.

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AndreTheGiant
Immortal
Immortal

There is a tradeoff between a lot of nodes into a cluster and few (but enogh) nodes...

With too many nodes you have some capacity problems for admission control.

With too much the cluster could be a little slower.

Also too much nodes on the same LUNs could be not the best choice.

IMHO I suggest to use cluster with 4-6 nodes.

Andre

Andre | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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russ79
Enthusiast
Enthusiast

Andre,

Can you describe what kind of admission control problems would arise? Have you had any experience with clusters greater than 6 nodes that makes you pick 4-6 as an optimum number? I know the max is 32 nodes per cluster, I wont be going anywhere near that number, I fully understand the issues that could arise from too much I/O on a lun and in fact this cluster would be using 3 to 4 different luns with no extents...

-Russ

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AndreTheGiant
Immortal
Immortal

Can you describe what kind of admission control problems would arise?

Less nodes = more resources problem when you have a fail

Have you had any experience with clusters greater than 6 nodes that makes you pick 4-6 as an optimum number?

With ESX 3.5 a good number is 5 (the max number of primary nodes). On ESX 4.0 this number is not so important, but the I/O problem and the number of ESX that insist on the same LUN can give a max realistic number smaller than 32.

For more info on how HA works:

http://www.yellow-bricks.com/2008/09/09/ha-primary-and-secondary-nodes/

Andre

Andre | http://about.me/amauro | http://vinfrastructure.it/ | @Andrea_Mauro
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