VMotion, the VMware feature that enables live VM migration between ESX hosts is one of the major attractions of vSphere and before that, VMware Infrastructure (or VI for short). It’s simply quite amazing to watch a VM continue operation and maintain sessions while moving from one host to another.

As cool as this is, we’re often asked, “How do we take that one step further, and perform VMotion between datacenters?” This, of course, is a non-trivial thing to do.  There is the challenge of moving a VM over distance (which involves some degree of additional latency) without dropping sessions. To maintain sessions with existing technologies means stretching the L2 domain between the sites–not pretty from a network architecture standpoint. And then there is the storage piece. If you move the VM, it has to remotely access its disk in the other site until a Storage VMotion occurs.

Last year, Cisco and VMware began the task of trying to solve these long distance VMotion issues with the target of seamlessly migrating a VM between two datacenters separated by a reasonable distance. The joint Cisco/VMware lab in San Jose has run number of tests over varying distances (simulated with reels of optic fiber) as a proof of concept. We will demonstrate this proof of concept at Cisco Live this week in San Francisco. The demo as it stands incorporates a distance of 80km (50 miles). That’s around 400us latency each way over fiber or a round trip just under 1ms.

This proof of concept is aimed at the following requirements:

  1. Load balance compute power over multiple sites: Migrate VMs between datacenters to “follow the sun”  or to simply load balance over multiple sites. Enterprises with multiple sites can also conserve power and cooling by dynamically consolidating VMs to fewer datacenters (automated by VMware Dynamic Power Management (DPM))—another enabler for the Green datacenter of the future.
  2. Avoid downtime during DC maintenance: applications on a server or datacenter infrastructure requiring maintenance can be migrated offsite without downtime.
  3. Disaster Avoidance: Data centers in the path of natural calamities (e.g. hurricanes) can proactively migrate the mission critical application environment over to another data center.

Use cases #2 and #3 above also require a Storage VMotion to move the disk image to the alternative datacenter.

Remember, this is a proof of concept, so we still have work to do in multiple areas. e.g. the storage VMotion for disaster avoidance and so on.

See and hear about it at Cisco Live this week…

Cisco Live is on this week in San Francisco. We will feature briefings in the VMware theatre (booth #531 …adjacent to the big Cisco booth). Refer to the theatre schedule posted at the VMware booth for session times. (of course, you can just come and ask us about it anytime)

See an update at VMworld in San Francisco—August 2009

We will demonstrate this again at VMworld ( in San Francisco in August where we will also hold a technical breakout session on VMotion between datacenters. This will cover the proof on concept, test results, and reveal a little more of our plans to solve some of the remaining issues. Look for this session in the Technology and Architecture track.