Microsoft postpones live VM migration for Hyper-V two more years

9:08 pm EDT September 8, 2008 - At a virtualization product launch today, Microsoft give a long-delayed demo of Hyper-V live migration, but then went on to slate the feature's eventual release for the next edition of Windows Server.

In showing the upcoming capability to a crowd of customers in Bellevue, WA, Bob Muglia, senior VP of Microsoft's server and tools business, suggested that in the Windows Server product which follows Windows Server 2008, users will be able to instantly migrate virtualized software deployments from one server to the next, for consolidation on the fly.

But the live migration demo may actually come as bad news to some data center admins, who have been looking forward to Microsoft adopting some form of live migration since 2006. Microsoft's first delay of this feature was announced 16 months ago, after the company had promised it for "Longhorn," which became Windows Server 2008. The feature was cut, said product managers at the time, in order that Hyper-V could meet its launch window; but then that window was later scooted to 90 days after Windows Server 2008's own launch.

A little over one year later, the feature may now be waiting for a launch date two years from now, at the earliest. Without mentioning a specific time today, Microsoft stated live migration would be ready for Windows Server 2008 R2, which it touted as the very next version of the server operating system. Yet this product roadmap updated last month clearly marks the R2 version as "scheduled for release during 2010."

Live migration may actually be a necessity for some data centers, especially for systems that use failover clustering. If a virtual machine is running on a system that fails, conceivably a former state of that machine could be restored from a backup, but that would take time. With live migration, data centers can relocate running instances of critical servers between physical processors, with zero downtime.

In the absence of live migration, this year, Microsoft had been trying to promote an alternative scheme it calls quick migration, not only as a substitute but possibly -- if you follow the logic -- something even better. "Using Windows Server Hyper-V and the quick migration capability," reads a January 2008 Microsoft white paper, "you can consolidate physical servers and, at the same time, maintain the availability and flexibility of business-critical services during scheduled maintenance, or quickly restore services after unplanned downtime."

With the quick migration scheme, Hyper-V can rapidly save the state of an active machine to disk storage, reassign that saved state to a new physical processor or cluster, and then re-activate that state without loss of activity, in a process that Microsoft describes as "minimizing downtime."

Minimizing, though not eliminating. The company's own engineers admit that, assuming everything else goes perfectly, downtime could be cut to as short as six seconds.

Though quick migration was billed as a new feature by Microsoft at the time the term was introduced, last year, a technical representative of Microsoft Ireland admitted straight out that quick migration was actually a renamed feature that appeared in Windows Server 2003, known then as host-level clustering.

So rebuttals of Microsoft's arguments by VMware and its supporters have typically referred to the feature by its original name, especially in comparison to VMware's VMotion live migration.

"Without live migration, any migration solution still involves downtime, and therefore can't really compete with VMotion. Host-level clustering is great, and something I'd love to see VMware tackle for those shops where VMware HA just isn't quite enough to meet SLAs [service-level agreements]," wrote IT administrator Scott Lowe in July 2007. "But host-level clustering is no substitution for VMotion."

In a series of April 2008 blog posts for Microsoft's virtualization team, lead program manager Jeff Woolsey delicately implied that Hyper-V's quick virtualization was actually more fail-safe than VMware's live migration, by giving administrators a picture of a single point of failure, and implying that quick migration avoids that fate.

"Virtualization actually creates a major problem: single point of failure," Woolsey wrote in Part 1. "Think about it. In the past, you may have been running 20 workloads each on their own physical server. When one of those servers goes down it's bad, but probably not the end of the world. In a virtualized environment, suppose you have 20 workloads running a top a single server. What happens when that physical server goes down? All 20 workloads go down. That's not bad, that's catastrophic."

In Part 2, Woolsey followed up with this: "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."

VMware, meanwhile, already has a live migration feature, which has been one of its major selling points to data centers -- and apparently will be for at least two years to come.

Next: Microsoft finally solves the Virtual Machine Manager debacle...