Set the Elastic DRS policy on a cluster to optimize for your workloads' needs.

In a new SDDC, Elastic DRS uses the Elastic DRS Baseline policy, adding hosts after storage utilization reaches 80% or if an availability zone failure occurs. You can select a different policy if it provides better support for your workload VMs. For any policy, scale-out is triggered when a cluster reaches the high threshold for any resource. Scale-in is triggered only after all of the low thresholds have been reached. See How the Elastic DRS Algorithm Works for more information about EDRS scale-out and scale-in logic.

Note: For two-host SDDCs, only the Elastic DRS Baseline policy is available.
The following policies are available:
Optimize for Best Performance
When scaling in, this policy removes hosts gradually in order to avoid performance slowdowns as demand spikes. It has the following thresholds:
Resource High Threshold Low Threshold
CPU 90% utilization 50% utilization
Memory 80% utilization 50% utilization
Storage 80% utilization 20% utilization
Optimize for Lowest Cost
When scaling in, this policy removes hosts quickly in order to maintain baseline performance while keeping host counts to a practical minimum. It has the following thresholds:
Resource High Threshold Low Threshold
CPU 90% utilization 60% utilization
Memory 80% utilization 60% utilization
Storage 80% utilization 20% utilization
Optimize for Rapid Scale-Out
This policy adds multiple hosts at a time when needed for memory or CPU, and adds hosts incrementally when needed for storage. By default, hosts are added two at a time, but beginning with SDDC version 1.14 you can specify a larger increment if you need faster scaling for disaster recovery and similar use cases. When using this policy, scale-out time increases with the number of hosts added and, when the increment is large (12 hosts), can take up to 40 minutes in some configurations. You must manually remove these hosts when they are no longer needed. This policy has the following thresholds:
Resource High Threshold Low Threshold
CPU 80% utilization 0% utilization (no scale-in)
Memory 80% utilization 0% utilization (no scale-in)
Storage 80% utilization 0% utilization (no scale-in)
Elastic DRS polices are based on two variables:
Minimum cluster size
The minimum host count that permits EDRS scaling. Once minimum cluster size is reached, EDRS cannot perform a scale-in operation, but you can still remove hosts manually until your organization’s minimum host count is reached.
Maximum cluster size
The maximum host count that permits EDRS scaling. Once maximum cluster size is reached, EDRS cannot perform a scale-out operation, but you can still add hosts manually until your organization’s maximum host count is reached.

Procedure

  1. Log in to the VMC Console at https://vmc.vmware.com.
  2. Click on the SDDC and then click Summary.
  3. On the card for the SDDC or cluster, click ACTIONS and choose Edit EDRS Settings.
  4. Select the Elastic DRS policy you want to use.
    The Elastic DRS Baseline policy has no parameters. For other policies, specify a Minimum cluster size of 3 or more and a Maximum cluster size consistent with your expected workload resource consumption. The Maximum cluster size applies to CPU and Memory. To maintain storage capacity and ensure data durability, the service can add more hosts than what you specified in Maximum cluster size.
  5. Click Save.