The Workload Balancing tool is available for solution providers to optimize server workloads between hosts in customer's XenServer Enterprise or Platinum environments. Using Workload Balancing ensures that a virtual machine (VM) will always runs on the host that can handle the workload best at that moment.
Because the Workload Balancing Administration Tool is a separate add-on, solution providers will need to start the installation program from a Windows workstation, which will make sure that required components, such as the database server, are available.
Setting up XenServer Workload Balancing Administration Tool
Workload Balancing needs a data store, which is in one of the supported database platforms, and an Apache Tomcat 5 server. Using SQL Express for installation with default options keeps things simple and after specifying the database to use, you can indicate that you want to use Windows or database authentication.
To set up Workload Balancing communication (which occurs over HTTPS port 8012 by default), you need to enter a user name or group name. You also need to set up an SSL certificate -- use an existing certificate or a self-signed certificate generated by the installation program.
Configuring Workload Balancing
After installing Workload Balancing, you will find the WorkLoadBalancing (WLB) tab in the XenCenter Resource pool. The WLB tab opens a wizard that sets up the essential parts of Workload Balancing. You need to specify the Workload Balancing server name, IP address, port and the credentials you have used while setting up the product. Solution providers should be aware that there are two sets of credentials that have to be entered: The credentials that XenServer uses to connect to the Workload Balancing server and the credentials that Workload Balancing uses to connect to XenServer. Both of these can be in Active Directory (AD) if you've set up your environment for AD authentication.
Once you've set up the basic parameters, set up the actual Workload Balancing solution. There are two modes to choose from: Maximized performance, which gives guaranteed performance metrics for the VMs on a host, and maximized density, which provides highest number of VMs on a host.
In the maximized performance mode, you need to select critical thresholds that specify the minimal hardware configuration that you want to have available for your VMs. It's a good idea to keep the default settings at first, and then use the reporting utility to learn which hardware resources are really used. By specifying the performance settings, you can specify the importance of each setting and, for instance, indicate that CPU performance is more important than the availability of RAM in your customer’s environment.
Once installed, Workload Balancing will recommend the best placement for a VM based on the environment’s performance settings any time a VM has to be placed somewhere. For example, if you start a VM, you'll get the default option for starting it on the most optimal server or to select an alternative server. You can see how well each server will be able to handle your workload by a performance rating, which is indicated as a number of stars.
Now that you've learned the requirements for optimized workload balancing in your environment, you can set up your resource pools accordingly. On a pool, you can set up a schedule that starts a maximized-performance policy every day at 8 a.m., which may involve running some additional XenServer hosts, and a maximized-density schedule at the end of the day. This allows your customer to cut their energy bill costs by saving on the amount of physical hosts that need to be up and running.
For customers with automated datacenters, Workload Balancing is an important feature that gives your customer’s virtualized environment the ability to find out which hosts have optimal resources available to run VMs. In a deployment where Workload Balancing is used intelligently, your customer can even save money because efficient VM placement can allow you to shut down actual physical hosts.
About the expert
Sander van Vugt is an independent trainer and consultant living in the Netherlands. Van Vugt is an expert in Linux high availability, virtualization and performance and has completed several projects that implement all three. He is also the writer of various Linux-related books, such as Beginning the Linux Command Line, Beginning Ubuntu Server Administration and Pro Ubuntu Server Administration.