NCI 7.5 Deep Dive – Part Two: Elastic VM Storage

With AOS 7.5, Nutanix expands its hybrid cloud capabilities with a powerful new feature: Elastic VM Storage. This enhancement allows Nutanix AHV clusters within the same Prism Central domain to share storage resources, giving administrators the flexibility in balancing compute and storage across the environment.

In this article, Part Two of our series, we explore what Elastic VM Storage is, how it works, and where it fits into real-world infrastructure design.

What Is Elastic VM Storage?

Elastic VM Storage allows one Nutanix AHV HCI cluster to serve storage to other AHV clusters, all managed under the same Prism Central domain. With this capability, VMs running on Cluster A can store their disks on Cluster B, effectively decoupling compute and storage within the Nutanix environment.

This brings new operational flexibility, including:

• Running compute-heavy workloads on clusters with available CPU

• Storing VM disks on clusters with more storage headroom

• Reducing the need for immediate hardware expansion

• Better balancing of resources across multi-cluster environments

This architecture is especially useful in environments where growth across clusters is uneven or where storage availability differs significantly between clusters.

How It Works

To enable Elastic VM Storage, administrators create a shared storage container on the cluster that will provide remote storage. This container is then made accessible to other clusters under the same Prism Central instance.

Once enabled:

• VMs on other clusters can attach disks stored remotely

• Storage I/O flows securely through the inter-cluster connection

• The remote container behaves like a native storage resource for those VMs

This keeps the operational model simple while providing more granular control over resource allocation.

Limitations and Requirements for Elastic VM Storage

Before deploying Elastic VM Storage, it is important to understand both the prerequisites and the functional limitations of this capability. The following combined list outlines things you must consider to ensure proper configuration, predictable performance, and reliable VM behavior across clusters.

Requirements and Prerequisites

• Prism Central Version: All clusters providing compute or storage must be registered to the same Prism Central instance running version 7.5 or higher.

• AHV Hypervisor Requirement: Elastic VM Storage is supported only on Nutanix AHV clusters. ESXi and Hyper-V clusters are not supported.

• Latency Requirement: Round-trip latency between the compute cluster and the remote storage cluster must be 5 milliseconds or less. If this threshold is not met, VM creation will fail to prevent performance degradation.

• Data Services IP Configuration: Each participating cluster must have a Data Services IP configured in Prism Element to enable cross-cluster communication and storage access.

• Replication Factor Requirements: Shared storage containers must be on storage configured with RF2 or RF3. RF1 is not supported for Elastic VM Storage.

• Single Storage Source Requirement:

  All VM disks must reside on one remote storage cluster. A VM cannot mix disks across multiple remote clusters or combine local + remote storage.

Functional Limitations

• Templates and OVAs: Elastic VMs cannot be created from templates or OVAs.

• Disaster Recovery Support:

  • Elastic VMs cannot be added to DR protection policies.

  • Application-consistent recovery points are not supported.

  • Recovery points cannot be created for VMs with vTPM enabled.

  • Elastic VMs cannot be reverted from any recovery point.

• Nutanix Guest Tools: Installing Nutanix Guest Tools (NGT) on Elastic VMs is not supported.

• Cluster Unregistration: A cluster providing or consuming Elastic VM Storage cannot be unregistered from Prism Central until all Elastic VM dependencies are removed.

• High Availability Behavior: If a host fails and the remote storage cluster becomes unreachable, the failover process for Elastic VMs will pause. It resumes automatically once connectivity is restored.

In Summary

Elastic VM Storage brings a new level of flexibility to Nutanix AHV environments by enabling clusters to share storage seamlessly within the same Prism Central domain. While the feature comes with some limitations in this first release, it opens the door to smarter resource utilization and more adaptable multi-cluster deployments.