Set the Elastic DRS policy on a cluster to optimize for your workloads' needs.
In a new SDDC, elastic DRS uses the Default Storage Scale-Out policy, adding hosts only when storage utilization exceeds the threshold of 75%. 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.
- Optimize for Best Performance
This policy adds hosts more quickly and removes hosts more slowly 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 70% utilization 20% utilization
- Optimize for Lowest Cost
This policy adds hosts more slowly and removes hosts more quickly in order to provide 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 70% 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 70% utilization 0% utilization (no scale-in)
- Log in to the VMC Console at https://vmc.vmware.com.
- Click on the SDDC and then click Summary.
- On the card for the SDDC or cluster, click Edit EDRS Settings.
- Select the Elastic DRS policy you want to use.
The Default Storage Scale-Out 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.
- Click Save.