With a growing number of customers migrating to alternative virtualization solutions, one of the most common questions is which storage options are available and what limitations they may have. This is important, as enterprises will always wish to reuse as much of their existing infrastructure as possible. OpenNebula provides a flexible and disaggregated storage subsystem that accommodates both software-defined storage (SDS) and traditional enterprise hardware storage appliances. This allows the platform to accommodate most existing storage options.

OpenNebula organizes storage into three structural Datastore Types:

• Image Datastore: Stores the master repository of VM disk images.
• System Datastore: Holds the operational, active disks for running Virtual Machines (usually cloned or symlinked from the Image Datastore).
• Files & Kernels Datastore: Stores plain text files used for contextualization, ram-disks, or specific hypervisor kernels.

Core Storage Options in OpenNebula Enterprise Edition

1. NFS/NAS Datastore (Shared Filesystem)

Assumes that hypervisor hosts can access a shared volume hosted on a NAS server (using NFS, GlusterFS, Lustre, etc.) to store master and active images.

• Advantages: Straightforward configuration, native support for thin-provisioning using the qcow2 format, and easy over-commitment of space.
• Disadvantages: Storage performance scales with and is bound by the hardware limits of the single or cluster NAS backend. High network I/O overhead.

2. Local Storage Datastore

Uses the local disks directly attached to each individual hypervisor host. Images are transferred dynamically via SSH or cached locally.

• Advantages: Extremely high I/O performance and low latency since traffic doesn’t traverse a shared storage network. Lower initial infrastructure costs.
• Disadvantages: Lacks native shared storage features, making features like live migration require a complete network copy of the disk, increasing VM migration times.

3. Ceph Datastore (Software-Defined Storage)

Fully integrated block storage (Ceph RBD) driver designed for massively scalable, high-performing distributed architectures.

• Advantages: Outstanding horizontal scaling, automatic replication, high availability, and support for instant zero-copy snapshots and cloning.
• Disadvantages: Complex to set up, monitor, and maintain. Requires significant hardware resource overhead (CPU/RAM) on storage nodes.

4. LVM SAN / LVM (File Mode) SAN Datastore

Designed for standard Storage Area Networks (SAN) utilizing Fibre Channel or iSCSI, where master files are transformed into block devices (LVM Logical Volumes) upon VM creation.

• Advantages: Raw block-level performance directly from standard SANs without requiring a clustered filesystem (like CLVM). Support for LVM Thin Provisioning.
• Disadvantages: Operations rely on metadata refreshes across hosts via SSH proxies; lacks sophisticated native appliance API hooks unless using dedicated EE drivers.

5. Everpure SAN Datastore (Enterprise Edition Exclusive)

A specialized native storage driver engineered to communicate directly with Pure Storage FlashArray blocks via the FlashArray REST API over iSCSI and multipath.

• Advantages: Offloads VM lifecycle tasks (provisioning, deletion, cloning) straight to FlashArray. Zero-copy snapshots cause flat read/write latency regardless of chain depth. Includes incremental SAN-snapshot backups.
• Disadvantages: Requires a dedicated Everpure FlashArray ecosystem; scoped strictly to primary block device provisioning.

6. NetApp SAN Datastore (Enterprise Edition Exclusive)

A native SAN integration designed explicitly for NetApp appliances, unlocking synchronous hardware-level operations.

• Advantages: High block-level performance and exclusive access to NetApp Incremental Backup support, which minimizes backup windows by only copying changed data blocks at the array level.
• Disadvantages: Vendor lock-in to NetApp hardware arrays.

7. Specialized Datastores (VirtioFS & RDM)

• VirtioFS: Allows VMs to directly interact with hypervisor-host filesystems for hyper-low-latency data sharing.
• Raw Device Mapping (RDM): Passes physical storage devices directly through to the guest VM.

How to Choose the Right Storage Backend 

Storage Option	Datastore Type / Protocol	Primary Advantages	Primary Disadvantages	Best Suited For
NFS/NAS	Shared File System (NFS, Gluster)	Simple architecture; default qcow2 thin provisioning.	Performance bottleneck at the NAS controller level.	Standard corporate clouds, development environments.
Local Storage	Host-local Disks (SSH/Local)	Extreme I/O speeds; very low cost; no shared fabric needed.	Storage live migration takes longer (must copy across network).	High-performance compute, ephemeral workloads, edge nodes.
Ceph RBD	Software-Defined Block Storage	Massive scalability; high fault tolerance; instant clones.	High operational complexity; resource-heavy.	Large-scale production clouds, private hyperconverged infrastructure (HCI).
LVM SAN	Block Storage (iSCSI / FC)	Fast raw block performance using generic SAN.	Relies on host-side SSH orchestration and LVM configuration.	Standard enterprise SAN environments running high-end block hardware.
Everpure SAN (EE)	Native API (Everpure FlashArray)	Instant zero-copy metadata clones; automated multipath; SAN backups.	Bound strictly to Everpure hardware ecosystem.	Mission-critical Tier-1 enterprise environments demanding predictable flat latencies.
NetApp SAN (EE)	Native API (NetApp Storage)	Hardware offloading; optimized block-level incremental backups.	Bound strictly to NetApp hardware ecosystem.	Enterprise setups heavily invested in NetApp solutions.
VirtioFS	Shared Host Filesystem	Low-latency shared file access between host and guest.	Scoped to specific data-sharing use cases; not a general backend.	Data-intensive workloads and container-virtual machine file sharing.

In summary, OpenNebula supports most existing enterprise storage technologies, enabling organizations to leverage their existing storage infrastructure while adopting an open source enterprise cloud platform without vendor lock-in.

Explore OpenNebula Enterprise Edition to learn more about supported storage backends, enterprise integrations, and migration options.