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VMConAWS About Elastic DRS and its Types / Limitation

Today's blog we talk about the Elastic DRS feature and is types /limitations.

What is Elastic DRS :

With Elastic DRS you can set policies to automatically scale your cloud SDDC by Adding or removing hosts in response to demand.

Elastic DRS replaces vSphere DPM in a VMware Cloud on AWS SDDC . One feature that further extends availability and resiliency of the SDDC cluster, which is exclusive to VMware Cloud on AWS, is Elastic DRS (eDRS).

Elastic DRS allows you to scale your cluster in response to demand, or lack of demand, by adding or removing hosts automatically based on specific policies that are configured.

The eDRS algorithm runs every 5 minutes and looks at predefined resource thresholds for CPU, memory, and storage. The thresholds cannot be changed by the user and differ based on the policy configured. While the algorithm runs every 5 minutes.

Below is the screen shot from my demo lab which has only 1 host. The screen shots show us to access the Elastic DRS Setting from the VMC on AWS SDDC Pane.

once you click Edit EDRS Settings - > That where you will see the EDRS types :

  • Default Storage scale out

  • Optimized for Best Performance

  • Optimize for lowers cost

  • Optimze for Rapid Scale out

Like shown below

Benefits of Elastic DRS Policies :

  • Automatically scale based on utilization

  • Enabled at the cluster level i.e. on SDDC Pane

  • Monitoring interval that is every 5 minutes

  • Scale up when any resources crossess a predefined threshold

  • Scale down when all resources consistently remain below thresholds

  • Multiple policies that can meet specific needs .

Default Storage scale out :

Enabled by default, add host only when storage utilization exceeds threshold . Scale-In is an manual process

Optimized for Best Performance :

Avoid performance slowdown as demand spikes . Adss host more quickly and it removes hosts more slowly.

Optimize for lowers cost :

Keeps hosts counts to a practical minimum and Add/ host quickly but remove hosts remove slowly.

Optimze for Rapid Scale out :

Perfect for DR or VDI Scaling. It Adds 4 hots in parallel for CPU and RAM. Also Adds 1 host for Storage . The Scale-in is a manual process here.

Each EDRS policy uses different resource thresholds to perform scaling events. Some of them require manual scaling process like we discuss above .

To Configure EDRS you select a policy , configure the minimum and maximum cluster sizes and click save button. The Dashboard of cluster pane will show u the EDRS policy .

Limitations of EDRS :

  • It is not supported on a single node SDDC .

  • If a user initiated add or remove host operation is in progress the current recommedattion by the EDRS algorithm is ignored.

  • After the user initiated operation completes the algorithm might recommend a scale-in or sclae-out operation based on the changes in the resource utilization and current policy profile.

  • If a user initiated add or remove host operation is started while a recommendation is being applied the operation fails with an error indicating concurrent update exception.

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