IBM code unchains virtual workloads

Some of the first fruits of a European Union-funded project led by IBM are making their way into the field of cloud computing, in the form of a virtual machine migration technology.

The technology, sprouting from the Reservoir (Resources and Services Virtualisation without Barriers) program, offers a way to move a live, virtualised workload from one server to another, without the need for the two locations to share the same storage space.

"We at IBM Research view this as a huge leap forward because the new open source code enables sharing across domains where shared networked storage and hardware components are not practical," wrote Dr. Yaron Wolfsthal, an IBM research senior manager of system technologies and services who led the development, in a blog post announcing the code.

"This is a technology for live service migration which obviates the need for shared storage between the source and target physical machines [which] was previously required by all known migration mechanisms," Wolfsthal said in a subsequent e-mail interview.

Of course, VMware has offered the ability to move a virtual machine from one server to another for a while now, by way of software called VMotion. But this approach has its limits: It requires both the source and the destination hosts to share the same storage device, which limits the range of migration. "To the best of our understanding, vSphere does not support live migration without shared storage," Wolfsthal said.

In fact VMware has been trying to solve the long-distance problem. Last year it said it was working with Cisco Systems on a proof-of-concept demonstration that it planned to show off at a Cisco event in San Francisco. "This, of course, is a non-trivial thing to do," VMware said at the time.

Others have commented on the single-storage-location limitation as well. "This means that inside a single data center, one can only move a [virtual machine] across a relatively small number of physical machines. Not exactly what the marketing guys would have you believe," wrote Alex Benik, a principal at analyst firm Battery Ventures, in a research note.

In contrast, the Reservoir technology involves copying the workload over to the new location while keeping it running using a delicately choreographed combination of push and pull replication mechanisms. "The movement is not restricted and virtual machines can be now moved from anywhere to anywhere," Wolfsthal explained. Both locations will need to have the code running in their hypervisors in order to make this migration work.

Thus far, the capability has been integrated into two open-source virtualisation programs. One is KVM (Kernel-based Virtualisation), a hypervisor technology that has been incorporated into the Linux kernel and is the cornerstone of Red Hat's virtualisation strategy. It has also been inserted into the Libvirt virtualisation toolkit, which supports both the Citrix Xen hypervisor and the VMware hypervisors.

Wolfsthal declined to talk about what, if any, plans IBM has for commercialising the technology.

Reservoir is a three-year European Union-funded program to develop new cloud computing, virtualisation and Web 2.0 technologies.