Bridging datacenters with VMware vSphere and IBM SAN Volume Controller – Part 3

VMware Stretched clusters is a concept that has gained popularity in recent years.  Two years ago at VMworld I remember a Cisco keynote where “Long Distance vMotion” was discussed as a future concept.  Long distance vMotion can be achieved within a Stretch Cluster, but Stretched cluster is not required for LD vMotion.

Here are a few things to mention first about VMotion…

-VMotion can execute between hosts of the same or different clusters.  They just must be within the same vCenter server.

-VMotion between clusters can only be completed manually and results in a loss of cluster attributes for the virtual machine (HA/DRS rules)

-VMotion within a cluster can be automatic (DRS) or manual and there is no loss of cluster attributes.

The concept of a Stretched VMware cluster is very similar to the stretched SVC configuration.  Each site contains hosts from the cluster.  Virtual machines can run at either site.  In the event of a failure VMware HA restarts affected virtual machines on hosts that are still available in the cluster.  Lastly virtual machines can be migrated with VMotion between hosts in the cluster either manually or automatically.

VMware stretched clusters have several requirements and restrictions.  Scott Lowe recently posted some slides from a presentation that he did on stretched VMware clusters.  I thought the slides presented the material well so I will link to his site.

So by combining Stretched SVC and VMware cluster you get a solution that looks like…

I had had to wait to publish this post until a few resources were available.

First – There is a white paper available which covers (in detail) the solution that I have discussed in these blog posts.  That white paper is available at this link:


Second – I can’t speak to what the previous support was like.  I know there is a large number of customers who are running this exact configuration and who have undoubtedly had support issues.  But I can verify that this solution is now fully supported by IBM and VMware.  The VMware KB can be found here:



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3 Responses to Bridging datacenters with VMware vSphere and IBM SAN Volume Controller – Part 3

  1. rogerluethy says:

    Very good articles. Thank you !

  2. rogerluethy says:

    Hi Rawley, in the Techdoc document and also the picture here in the blog shows a SVC Stretched Cluster with 2 IO-Groups. To my knowledge you have just one Node one each side and not a pair as shown here, right ? Cheers, Roger

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