Fully automated DRS places hosts into maintenance mode without taking into account potential resource pool violations
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Fully automated DRS places hosts into maintenance mode without taking into account potential resource pool violations

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Article ID: 340964

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Updated On:

Products

VMware vCenter Server

Issue/Introduction

Symptoms:
During patching by vSphere Update Manager or NSX-v host/cluster upgrade, fully automated DRS can select hosts to enter maintenance mode without taking resource pool reservations into account. This could result in VM power-on failures while the upgrade or patching activity is in progress.

Environment

VMware vCenter Server 6.5.x
VMware vCenter Server 6.7.x
VMware vCenter Server 6.0.x

Cause

Current vSphere DRS design does not take into consideration resource pool reservations when choosing hosts to be place into maintenance mode.

Resolution

Currently there is no resolution and is expected behaviour.

Workaround:
Ensure the DRS Automation level is set to manual before starting the patching or upgrade process. For NSX upgrades via EAM, one possible workaround is to limit the number of hosts that can be put into MM by using the EAM option.

Procedure

  1. Browse to a cluster in the vSphere Client.
  2. Click the Configure tab and click Services.
  3. Under vSphere DRS click Edit.
  4. Under DRS Automation, select a default automation level for DRS.

    Automation Level

    Action

    Manual

    • Initial placement: Recommended host is displayed.

    • Migration: Recommendation is displayed.

    Partially Automated

    • Initial placement: Automatic.

    • Migration: Recommendation is displayed.

    Fully Automated

    • Initial placement: Automatic.

    • Migration: Recommendation is run automatically.

  5. Click OK
Note: Do not disable DRS. 

When DRS is disabled, the cluster’s resource pool hierarchy and affinity rules are not reestablished when DRS is turned back on. If you disable DRS, the resource pools are removed from the cluster. 


Additional Information

Impact/Risks:
Virtual machines may fail to power on. Although resource pool reservations are not counted, resources of powered on virtual machines are not impacted. 

Avoid powering on virtual machines which will have a large demand on resources or which have reservations while the upgrade or patching is ongoing.

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