Storage DRS fails to balance VMDKs across Datastore Cluster in ESXi 8.0.x

Products

• VMware vSphere ESXi

Issue/Introduction

Virtual machine disks (VMDKs) are not automatically balanced across member datastores within a Datastore Cluster. This results in uneven capacity utilization, where one datastore may reach maximum capacity while others remain underutilized. Storage DRS (SDRS) recommendations are either not generated or fail to execute storage migrations.

Environment

VMware vSphere ESXi 8.x
VMware vCenter Server 8.x

Cause

Storage DRS automated load balancing is blocked or restricted by one or more of the following configurations: default Intra-VM affinity rules (which enforce keeping all VMDKs of a VM on the same datastore), manual VM-level automation overrides, the presence of independent virtual disks, incompatible NFS 4.1 I/O metric settings, or invalid VM resource allocation limits.

Resolution

o restore Storage DRS load balancing functionality, validate and adjust the following configurations:

1. Disable Default Intra-VM Affinity Rules:

   • Navigate to the Datastore Cluster > Configure > Storage DRS.

   • Click Edit > Advanced Options.

   • Uncheck Default VM affinity (Keep virtual disks together by default).

   • Click OK.

2. Revert VM-Level SDRS Overrides:

   • Navigate to the Datastore Cluster > Configure > VM Overrides.

   • Identify any VMs with an automation level set to "Manual" or "Disabled."

   • Select the affected VMs, click Edit, and change the automation level to Default (Fully Automated).

3. Remediate Independent Disks:

   • Storage DRS does not support automated live migration for independent disks.

   • Review VM hardware settings. If independent disks are present, change the disk mode to dependent or power off the VM to perform a cold migration.

4. Disable I/O Metrics for NFS 4.1 Datastores:

   • If the datastore cluster is backed by NFS 4.1, I/O-based load balancing is natively unsupported in vSphere 8.0.

   • Edit the Storage DRS settings and uncheck Enable IO metric for SDRS recommendations.

   • Under Advanced Options, set EnforceIOReservations = 0 and EnableIoLoadBalancing = 0.

5. Validate VM Resource Allocation Limits:

   • Storage DRS allocation checks will fail if a VM has a CPU or Memory allocation limit set to exactly 0.

   • Review VM settings across the cluster and ensure CPU and Memory limits are set to "Unlimited" or a valid non-zero value.

Additional Information

 

• KB 425804 - Storage DRS causing automated migration of VMDKs back to original location after Storage vMotion

• KB 430194 - Storage DRS does not migrate virtual machines despite meeting automation thresholds

• KB 422078 - Error: "Storage DRS is unable to move independent disks"

• KB 403952 - Storage DRS Does Not Generate Recommendations for All NFS 4.1 Datastores

• KB 400461 - Storage vMotion for VMs in a Datastore Cluster fails with Error