Blog

When was the last time you thought VMotion was a bad idea?

By Harley Stagner | Jun 17, 2010 | Insights, Virtualization

I read a blog post over at Windows IT Pro recently that prompted this post. Mr. Greg Shields asks the question “When was the last time you VMotion-ed?”

To answer your question Mr. Shields, I did it just this morning and once this afternoon. Nobody even noticed.

Mr. Shields goes on to quote one of his clients:

Well, we thought about that. But we found that we really don’t use VMotion pretty much ever. We know that we can use VMotion, and sometimes we do. But, our performance is acceptable so we don’t need DRM, and we find that that we’re really never doing activities that require us to relocate or re-balance our virtual machines.

With a followup to this:

That response really got me thinking about the uses of VMotion in contrast with all the publicity its feature gets in the IT press:

  • You use VMotion prior to rebooting a host.
  • You use VMotion to re-balance load (often through DRM’s automated processes)
  • You use VMotion’s HA after an unexpected failure.

Since Mr. Shields didn’t mention a product that does not have a feature like Distributed Resource Scheduler (hence, the argument against it), I won’t either. However, considering the source, I can tell you that it is probably a Redmond-based product.

So, here is my response to Mr. Shields, since he asked:

Just a few small points to clarify for those new to VMware that may be reading this.

First, VMotion and HA are two different things. You don’t use “VMotion’s HA”.

HA or High Availability is when you have a host failure (for unplanned downtime).

VMotion is a live migration (for planned downtime such as maintenance). I find that those new to VMware get these two confused all the time.

DRS (Distributed Resource Scheduler), not DRM (Digital Rights Management?) is a feature that VMware uses to balance the load across the cluster of available host resources utilizing the VMotion functionality.

Having cleared up those few items, here is my perspective.

My clients like being able to use VMotion to do maintenance during normal business hours on their hosts. I see it all the time.

My clients also enjoy not worrying about performance at the host level (like you would do in the physical world) by utilizing DRS. As long as they have enough resources in the cluster and their virtual infrastructure architecture is properly designed, they don’t have to worry about manually placing or load balancing their VM’s on certain hosts.

In summary, I’m all for VMotion and DRS. You can leave DRM in iTunes. I buy all my music DRM free from Amazon anyway .

Leave a Reply

Your email address will not be published. Required fields are marked *