Most virtual machines on Nutanix AHV use ordinary virtual disks attached directly to the VM. That model is simple and works for most applications. Some workloads, however, need storage with a lifecycle separate from the VM, shared access across multiple systems, or block access from a physical server. That is where Nutanix Volume Groups become useful.
A Volume Group is a logical collection of one or more virtual disks. Administrators manage the disks as a related unit and can attach the group to a VM or expose it through iSCSI.
Why use a Volume Group?
Volume Groups are useful when an application needs one or more of the following:
- Data disks managed separately from the VM boot disk
- Shared-disk access for a clustered application
- Block storage for a physical server
- Application data protected and cloned independently
- Multiple virtual disks grouped into one administrative object
Database platforms are a common example. Separating database disks from the operating system can simplify protection, cloning, and lifecycle operations.
Direct attachment on AHV
With direct attachment, a Volume Group is connected to an AHV VM and its disks appear as SCSI devices inside the guest operating system. AOS handles path resilience and storage access behind the scenes.
This approach has several benefits:
- No guest iSCSI configuration
- No dedicated storage network inside the guest
- Support for VM migration within the cluster
- A straightforward Prism-based workflow
Direct attachment is available for AHV workloads on the same cluster as the Volume Group. It is often the simplest choice when a virtual machine needs separate block devices but does not need access from outside the AHV cluster.
iSCSI access
Nutanix Volumes can expose a Volume Group as an iSCSI target. This makes the storage available to virtual or physical systems with a supported iSCSI initiator.
iSCSI is appropriate when:
- A physical server needs Nutanix-hosted block storage
- The consumer is not an AHV VM on the local cluster
- The application design already uses guest-managed iSCSI
- Network-level control of storage sessions is required
Because the guest or physical host manages the iSCSI session, administrators must plan initiator access, network paths, multipathing, and authentication.
Shared-disk workloads
A Volume Group can be shared by multiple VMs for supported clustered applications. Examples include database clusters that coordinate access to shared disks.
Shared storage does not remove the need for application-level coordination. The guest operating systems and clustering software must understand how to safely arbitrate access. Attaching the same writable disk to unrelated servers without a cluster-aware file system can corrupt data.
Before using shared attachment, confirm:
- The application and guest OS combination is supported
- The cluster software is configured before enabling writes
- Backup software understands the shared-disk layout
- Failure and recovery behavior has been tested
Protection and operational considerations
Decoupling application data from a VM can be powerful, but it changes the protection model. Make sure snapshots, replication policies, and recovery procedures include both the VM and its Volume Groups.
Also document disk ordering and guest mount points. A group may contain many disks, and an application may depend on a consistent relationship between the Nutanix disk, the guest device, and the application path.
Summary
Use standard VM disks for ordinary workloads. Consider Volume Groups when storage needs an independent lifecycle, shared access, physical-server connectivity, or application-specific protection.
For AHV VMs, direct attachment keeps the design simple. Use iSCSI when the storage consumer sits outside that model. Shared attachment should be reserved for supported, cluster-aware applications.
Related reading: Discovering Nutanix: Nutanix Unified Storage (NUS) shows where Volumes sits alongside Files and Objects. What’s New in Nutanix Prism Central 7.6, AOS 7.6, and AHV 11.2 covers the current platform release.
Sources:
- Nutanix Volume Groups v4 API reference, Nutanix Developer Portal
- Nutanix Volumes product overview, Nutanix
Are you using Volume Groups for databases, physical servers, or another workload? What operational lesson would you add?
Let me know in the comments below.