Virtualization users can migrate live virtual machines (VMs) across physical servers as long as those machines use the same processor generations. But now Advanced Micro Devices Inc. (AMD) is pushing virtualization software vendors to remove that limitation.
To loosen the live-migration constraints, Sunnyvale, Calif.-based AMD released a white paper disclosing details about AMD-V Extended Migration, a feature dating back to the first-generation Opteron processor that enables virtual machines to migrate between different versions of AMD processors.The need for migration ease
"Our customers are very interested in doing live migration because of the flexibility it provides," said Margaret Lewis, director of commercial solutions at AMD. "[AMD-V Extended Migration] is where the rubber meets the road. We've made this interface on the hardware end, but it is up to software to implement it."
AMD-V Extended Migration masks the differences between CPU generations, facilitating the safe live migration of virtual machines between servers running different generations of AMD processors. This includes existing single- and dual-core processors and all future AMD processor revisions, including the upcoming Barcelona quad-core AMD Opteron processor that is expected to be released Sept. 10.
AMD is reportedly working with various virtualization providers, including KVM, Novell Inc., Red Hat, Sun Microsystems Inc., Virtual Iron, VMware Inc. and XenSource Inc. to create compatible software for live migration of virtual machines across servers running AMD Opteron processors C, D, E, F, Barcelona and beyond.
In June, Intel Corp. announced a new feature called VT FlexMigration to enable live migration between different generations of Intel processors. Live migrations are possible with Woodcrest-, Clovertown- and Penryn- based machines, according to Intel spokesperson Nick Knupffer.
Users with AMD and Intel servers still won't be able to run live VMs across enemy lines – from an AMD-based server to an Intel based-server, or vice versa.Hardware is ready, but software lags
While Intel and AMD announce these hardware capabilities and attempt to squash any reluctance about upgrading to their next generation of processors, VMware has yet to publicly announce a product that enables live migrations among different processor families. VMware did not respond to questions about VMotion limitations by press time.
When it comes to live migrations, most users are unaware of the limitations of different processors Lewis said.
"Lots of users don't understand the dos and don'ts of live migration. You have to think about all the components: Servers have to be on a shared storage infrastructure, they have to have the same-generation processor, and other infrastructure considerations," said Lewis. "For [AMD-V Extended Migration] to become widely used we have to have people understand everything about it, and work with software vendors to make live migration as flexible as possible."
To do a live migration with VMware, for instance, each physical host server is required to have VMware Infrastructure 3 Enterprise installed with VirtualCenter and VMotion, which is an additional cost. Hosts must share storage area network infrastructure and use a single Virtual Machine File System (VMFS) volume. The host should also share a private Gbit migration network and systems must have the same processor types (AMD or Intel) with restrictions between processor families, according to AMD.
But other virtualization software providers can already take advantage of AMD-V Extended Migration and Intel VT FlexMigration.
Virtual Iron's Tim Walsh, the director of corporate marketing, said that with Virtual Iron's tools, users can migrate live workloads across the AMD Opteron processor family where (AMD-V) is in place.
"There are no limitations other than this. Every new AMD-based server shipped since last year has this capability," Walsh said. "We also do this today across the entire Intel x86 family, specifically Xeon 3100, 5100, 5300, 7100 and soon to be announced 7300 series [Caneland]."
For software without the capability to move VMs across servers with different processors, cold migration is the option. In cold migrations, virtual machines are powered off and the VM is moved from one physical machine to another.
Since different virtualization providers have different requirements for live migration, users should contact their virtualization software provider to find out constraints, Lewis said.
"We cannot [address] the software vendor roadmaps and when they will be able to do this, but the hardware is ready," Lewis said.AMD gives VMs freedom to move
To beat the system and move VMs across different processor families, CPU IDs and certain registers are masked, so the VM still thinks it is running on the processor it came up on, said Tim Mueting, AMD virtualization solutions manager.
There are a number of unsupported masks out there that are not endorsed by virtualization software vendors. AMD shows users how to write their own masks in the white paper, but software vendors may not support users' efforts to write their own masks, Mueting said.
"This puts a level playing field in the pool of resources among multiple processors, but it is up to the software vendors to implement," Mueting said. "Right now there are CPU masks that give users certain capabilities. In the end, virtualization software vendors need to support it, because there are certain environments that users still cannot migrate between."
And, Mueting continued, "When customers start looking at new hardware and servers, they wonder if they can put them in the same pool and be able to 'VMotion' or 'XenMotion' off their old hardware onto the new hardware. It is becoming an issue from a planning standpoint; most people are thinking ahead now, because [processor] changes happen so quickly."
Let us know what you think about the story; email Bridget Botelho, News Writer.
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