Distributed Resource Scheduler (DRS)

What It Is: VMware Distributed Resource Scheduler (DRS) automatically load balances resource utilization across a cluster of ESX hosts by using VMotion to migrate virtual machines from a heavily utilized ESX host to a more lightly used ESX host. VMware DRS analyzes the CPU and memory consumption of a virtual machine over time to determine whether to migrate it.

Use Case: Redistribute Virtual Machines off of an ESX Host during Maintenance

VMware DRS migrates virtual machines off of an ESX host when a user enters that host into maintenance mode. DRS will intelligently migrate virtual machines to other available hosts in the DRS cluster in a load-balanced manner. After the maintenance on that host is completed and the user takes it out of maintenance mode, DRS will then migrate virtual machines back onto the host.

Step 1: 

Turn On VMware DRS for a cluster.

In this step, you will turn on VMware DRS for a cluster of ESX hosts that you created earlier. To turn on VMware DRS on your cluster see Figure

1. Right-click the cluster and select Edit Settings.Under Cluster Features select Turn On VMware DRS. Each host in the cluster will now be configured for VMware DRS. Please note that you will need cluster administrator permissions to edit the cluster settings.

 

Step 2: Set automation level for DRS cluster.

In this step you will be able to configure your DRS cluster to automatically balance your virtual machines across the cluster or simply provide recommendations to the user on where to migrate the virtual machines to achieve a load balanced cluster. Configuring the automation level of VMware DRS for the cluster is shown in Figure. You can also configure the automation level for each virtual machines within the cluster—explained in Step 3 below.

1. Click VMware DRS in the cluster settings window and you will notice that the automation level is set to Fully automated by default. The fully automated level optimally places virtual machines within the cluster upon powering them on, as well as migrates virtual machines after power on to optimize resource usage. You can adjust the sensitivity of the automated level by moving the slider bar to more conservative or more aggressive.

2. The partially automated level only places virtual machines within the cluster upon power on and then gives recommendations on where to migrate them to optimize resource usage.

3. The manual level gives placement recommendations at power on as well as where to migrate them later.

For this evaluation leave your VMware DRS settings at the default of Fully automated with the Migration threshold set in the center level.

 

Step 3: Set automation level for each virtual machine.

In this step, you will be able to configure each virtual machine, to be automatically balanced across the cluster or simply provide recommendations to the user on where to migrate the virtual machine to achieve a load balanced cluster.

1. To adjust the automation level for each virtual machine, click Virtual Machine Optionsunder “VMware DRS” in the cluster settings window. For this evaluation keep your Virtual Machine Options set at their default values.