Transforming the Datacenter


Workloads in Motion

Workloads in Motion

Summary: When there is an outage or spike in user activity, you don’t have the luxury of a long runway. It becomes necessary to make changes on-the-fly, even automatically in some cases, so that there is no human latency at all, and that is where workload mobility comes in.

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TOPICS: Data Centers
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Some technology changes arrive gradually and predictably. You can foresee that a storage system is approaching its capacity limits, or that servers are approaching end-of-life, or that the datacenter is simply too small for next year’s workload. However, when there is an outage or spike in user activity, you don’t have the luxury of a long runway. It becomes necessary to make changes on-the-fly, even automatically in some cases, so that there is no human latency at all, and that is where workload mobility comes in.

Workload mobility, instrumental in managing gradual change, is absolutely critical for handling rapid change. Operating an efficient and highly available datacenter is not trivial, particularly when it involves complex, distributed applications. Fortunately, virtualization at the server, storage, and networking layers helps to create a layer of abstraction that greatly simplifies the task.

As datacenters grow in scale and aggregate dynamic resource pools, they must be able to balance their loads in response to changes in respective utilization. Workload mobility allows infrastructure managers to relocate computational processes in order to optimize data affinity. Administrators can also use the capability to free up critical resources in order to perform planned maintenance.

So how do you do it? There are several techniques that an enterprise can use in order to achieve these objectives. The easiest one is to implement a clustering technology and take advantage of its native failover capability. Clusters can transfer workloads almost instantly and also have other benefits such as ensuring high availability, making them ideal for mission-critical services. 

The downside? Clusters are expensive to implement and more complex to set up, so they are not the best option for every application. A more common approach is to set up both the source and target machine to use shared storage and then allow the virtual machine manager to replicate the compute instance to the target and redirect network traffic. Modern hypervisors have live migration capabilities that automate this task, which involves copying the running state of the virtual machine along with its in-use memory.

Shared-nothing live migration is a relatively new variation of this, but with some compelling advantages. It makes it possible to move a virtual machine from one host to another without any shared storage. Instead, it uses a high-speed network to copy the virtual hard disks and configuration metadata first and then completes the redirection in the traditional manner. Microsoft has a Shared-Nothing Live Migration feature that enables this.

This approach is the only solution for physical machines with direct attached storage, and it increases the options for high-end systems, including clusters, because there is no need for the source and target to share the same storage.

All of these capabilities allow an enterprise to optimize the datacenter on an on-going basis. The business demands and external environment are in constant flux. It is imperative for the technology to keep pace. One element of this agility is the ability to migrate workloads. In my next post, I will look at dynamically restructuring the underlying storage.

Topic: Data Centers

John Rhoton

About John Rhoton

John Rhoton is a contributor to CBS Interactive's custom content group, which powers this Microsoft sponsored blog. He is a technology strategist who specializes in consulting to global enterprise customers with a focus on cloud computing.His tenure in the IT industry spans over twenty-five years at major technology companies, defining and implementing business strategy. He has recently led corporate technical strategy development, business development, and adoption of cloud services, datacenter transformation, mobility, security and next-generation networking, while also driving key corporate knowledge management and community-building programs.John is the author of six books.

John Rhoton's views are his alone and do not necessarily represent those of Microsoft or CBSi.

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3 comments
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  • VMware also has this...

    As of V5.1

    http://blogs.vmware.com/vsphere/2012/09/vmotion-without-shared-storage-requirement-does-it-have-a-name.html
    jamfuse
  • Actually looks like it's available in Xen and KVM hypervisors as well...

    ..although it looks like the OpenStack team are pushing to have the KVM version of the functionality rebuilt with some improvements. Didn't know that, we use VMware at present.
    jamfuse
  • Re: VMware also has this...

    Hi jamfuse - thanks for the additional references.

    Best regards,

    John (@johnrhoton)
    johnrhoton