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Can you Vmotion between different physical data centers?

Chad Sakac has a great post on his Virtual Geek blog titled The Case For And Against Stretched ESX Clusters. In this post Chad discusses the possibilities of configuring ESX Clusters between 2 different physical data centers. That is, spanning the SAN across a wide area network so that VMs can be vmotioned between sites. The concept is a frequently discussed desire of many administrators, and Chad brings to light some great points for and against this design with specific configuration details about making it work with VMware ESX.

For example, the post explores several options:

  • Option A: is to literally just stretch the storage fabric and have the storage at one side – but man, you better have insane connectivity between sites, and this is at severe risk to “smoking hole” site failure – say bye-bye to your array.
  • Option B: is to use something like EMC Invista, Yotta Yotta or the like, and have a distributed synchronous LUN with two storage arrays.
  • Option C: some vendors (Lefthand Networks comes to mind) have a neat trick where they are in essence doing software RAID across x86 platforms on which they run software – so the RAID mirror node can be remote, and “take over” if you lose a site.
  • TIP: do the math. Regardless of which method is used, and even if you use compression – it’s a huge amount of bandwidth. My favorite analogy is to ask a customer to stick in a USB flash drive into their laptop, copy a big file and looking at the throughput. “

Chad goes on to point out that he feels stretching ESX Clusters is a bad idea in general and lists 4 solid reasons to support why. Check out all the whole post at the link above.

BTW, Chad revealed that he is the originator of the ESX home lab hardware shopping list I posted about back in March, and you can also see his original post titled Building a Home VMware Infrastructure Lab at his Virtual Geek blog as well.

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