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Things that make you go hmmmm – April 25, 2008

April 25th, 2008 |

Author: Rich Brambley

This weeks edition is centered on the topic of quick migration versus VMware HA and VMotion. We start with a post from the Windows Virtualization Team’s blog site and then explore some responses from a couple popular blogs in the virtualization community. Finally, if you have not seen Microsoft’s Quick Migration in action then check out the video at the end of this post. Links to the full posts are provided by clicking the section titles. Enjoy!

Windows Virtualization Team Blog : HYPER-V QUICK MIGRATION & VMWARE LIVE MIGRATION PART 2…

“After my last blog I received almost two dozen email telling me that VMotion was far superior for unplanned host downtime and that it was a much better HA solution because it could live migrate virtual machines. I’ve heard this fallacy espoused for many years and, folks, this simply isn’t the case.

In the case of unplanned downtime, VMotion can’t live migrate because there is no warning. Instead you must have VMware HA configured and the best it can do is restart the affected virtual machines on other nodes which is the same as what is provided with Windows Server 2008 Hyper-V and Failover Clustering.”

I can’t decide if Jeff from the Windows Virtualization team is trying to spin the Quick Migrate feature of Hyper-V as an equivalent for VMware Vmotion or if he just doesn’t understand the difference of HA versus VMotion and the need for planned host downtime without user interruptions.

In response to Jeff’s post there have been several interesting posts by the virtualization community.

MS Virtualization blogs and VMotion

“Indeed Microsoft can do the same with the use of Clustering. But can you live migrate virtual machines when a server needs maintenance? No, at this moment that’s not possible. In other words, you will have to wait for a suitable moment… planned downtime, probably after business hours. But in a 24×7 environment will there ever be a suitable moment? Even when your business isn’t 24×7, if there’s a possible hardware failure would you want to wait? But when you have a 8:1 consolidation ratio you probably will not be the most popular system engineer when “quick migrating” the file server or the mail server especially when these VM’s have a lot of RAM assigned.”

Duncan’s post over at Yellow-bricks.com illustrates the differences between HA features and VMotion rather nicely.

How far can VMware push the envelope?

“I found it funny because there really is no comparison at this point. Quick migration is maybe quick, but it is not live meaning like Vmotion. It got me thinking how far behind Microsoft really is and with some of the things coming from VMware in the near future how far ahead can they push it?”

Clint from Virtual Enthusiasm chimes in on the maturity of VMware’s features compared to the rest of the market.

A classic case of moving the goalposts

“You see Microsoft [is] accusing VMware of producing technology that does what it says in the book. Perhaps Microsoft should take a leaf out of VMware’s book for a change! Does Microsoft dare to claim that QuickMigrate is different and is there for availability[?] I think not, because you should never take a hammer to [do the] job of spanner.”

“So HA is not Continuous HA. Agreed. That’s why VMware have been working on continuous HA as demo’d at VMworld 2007. The founder of VMware pulled out the power – and the VM just kept running on another ESX host.

The real argument should be about Continuous HA vs MSCS.”

Mike at RTFM Education’s point is that if you can’t win the argument as is then change the discussion slightly so your answers will look better.

If you need a refresher on the VMWorld demonstration of Continuous HA then check out VMWorld.com’s:

Mendel’s continuous availability demo at VMworld

From the summary section of the post provided by Scott Lowe:

“The demo involved a pair of virtualized Exchange servers with some clients running LoadSim to generate a load against the virtual Exchange servers. The setup created “mirrored VMs”. As a demonstration of the technology, Mendel pulled the power plug on one of the ESX servers, and the secondary VM and clients barely even noticed the failure. Very nice technology!”

Just to give everyone a visual of what the discussion is all about, check out this video of a Hyper-V Live Migration from VMware TV:

Hyper-V Quick Migration breaks network connections

Go to blip.tv to see this video as well as VMware TV’s other video titled VMware VMotion does not break network connections.