VM cluster approach improves virtual machine performance

Although virtualization provides organizations with a tremendous amount of flexibility, some mission-critical workloads still rely on virtual machine cluster techniques to boost virtual machine performance

    Requires Free Membership to View

and availability.

As with traditional physical servers, virtual machines (VMs) can also be clustered. A VM cluster starts with two or more physical servers; we'll call them Server A and Server B. In simple deployments, such as a VMware ESX cluster, if Server A fails, its workloads restart on Server B using VMware VMotion. But there is still some downtime between the failure of Server A and when its workloads restart on Server B. VMware Distributed Resource Scheduler and other tools can help balance virtual workloads between physical servers to prevent Server B from becoming overburdened.

A more recent and aggressive alternative is to employ redundant VM hosts on different physical host servers to improve virtual machine performance. For example, one instance of a workload is deployed on Server A, and a redundant copy of that workload is deployed on Server B. The servers within the VM cluster are interconnected with dedicated "heartbeat" signals, and the workloads are synchronized using high-availability software. In this case, if Server A fails, the redundant VM host instance on Server B picks up immediately with almost no downtime for users.

When configuring a VM cluster, it may be beneficial to establish a resource pool across the physical host servers. CPU, memory and other resources are defined and added to the pool, then allocated among the VM hosts to ensure that adequate computing power is available to each virtual workload. Otherwise, a workload with inadequate computing resources may perform poorly, become unstable or even crash.

Administrators can also leave some resources unused in case the computing demands of particular virtual workloads change. For example, if a certain VM needs more CPU cycles than the amount already assigned, more can be taken from the unused resource pool. Of course, there needs to be a limit on the resources that each VM can take.

Administrators have no way of knowing when trouble occurs with servers or resources, so it's important to invest the time and effort in configuring alarms for a VM cluster and its resources. Similarly, it's important to configure alarms for any time the resource pool runs low or any time a VM host demands excessive resources.

This was first published in January 2010

There are Comments. Add yours.

TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to:

Disclaimer: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.