HCX migration warning: "None of the datastores under cluster satisfy storage space requirements for this batch"

Products

• VMware HCX

Issue/Introduction

During a VMware HCX bulk migration, the following warning appears in the HCX migration validation screen:

Warning: "None of the datastores under cluster satisfy storage space requirements for this batch on [cluster name]"

Individual datastore entries display the message:

"Requested storage is not available on datastore. Requested (includes storage policy overhead): [size] MB, Free space on storage - [datastore name]: [available space] MB on [datastore name]"

This warning appears when the total requested storage for a migration batch exceeds the free space on any single datastore within the destination cluster, even though the cluster collectively has sufficient storage capacity.

This is a warning-level validation message and does not prevent the migration from proceeding. The warning serves as a notification that no single datastore can hold the entire batch, but it does not block migration when the cluster collectively has adequate capacity.

Environment

• VMware HCX 4.x
• VMware vSphere ESXi 8.x
• VMware vCenter Server 8.x

Cause

HCX evaluates storage space requirements on a per-datastore basis rather than at the cluster level. When the total requested storage for a migration batch (including storage policy overhead) exceeds the free space on any individual datastore, HCX generates this warning for each datastore that cannot satisfy the full batch size.

Additionally, HCX storage calculations have a known behavior with concurrent migrations. If migrations are already pending against the same datastores when a new migration group is created, HCX measures all currently migrating VMs and the new VMs against the datastore's available space as reported at that moment. It does not account for space already consumed by pending migrations, which results in an over-calculation of the required storage. This can lead to inaccurate space reporting when multiple migration waves overlap on the same datastores. This over-calculation behavior is by design — HCX cannot predict the amount of data change that occurs on a VM during migration, so it intentionally over-allocates space as a safeguard to prevent datastore exhaustion mid-migration.

Resolution

This warning can be safely bypassed when the following conditions are confirmed:

1. Verify that the destination cluster has sufficient total free space across all datastores to accommodate the migration batch, including storage policy overhead.
2. Confirm that no other HCX migrations are actively pending or in-progress against the same set of destination datastores. If other migrations are pending, the storage calculation may be inaccurate due to the over-allocation behavior described above.
3. Proceed with the migration. The warning does not block the migration from completing successfully when the cluster-level capacity is sufficient.

Best practices for large-scale migrations to avoid storage calculation issues:

• Migrate all VMs to a given set of datastores in a single group and stagger the switchover times within that group.
• Alternatively, wait for a migration group to fully complete before creating another group or wave targeting the same datastores.
• Avoid creating multiple concurrent migration groups against the same datastores, as this increases the risk of inaccurate storage calculations.

If migrations fail due to storage errors after following these steps, contact Broadcom Support for further assistance.