Full HCI vs Disaggregated Architecture: A Buyer's Guide

In full HCI, every node in the Nutanix cluster contributes both compute resources and storage capacity to the pool. The Nutanix Distributed Storage Fabric manages all storage across nodes in software. Adding a node adds both compute and storage simultaneously. Management is unified under Prism Central - a single interface for VMs, storage, cluster health, and protection domains.

In disaggregated architecture, the Cisco UCS nodes are compute-only. They run Nutanix AHV and connect to a separate Pure FlashArray over a dedicated NVMe-oF storage network via Arista leaf switches. Storage and compute scale independently. Management spans three planes: Prism Central for compute and virtualization, Pure1 for storage, and Cisco Intersight for UCS lifecycle management.

The operational experience of both environments under Aegis is similar from the client perspective. IVI owns the platform operations in both cases. The architecture choice drives the procurement model, the scaling behavior, and the performance characteristics - not the day-to-day operations burden.

Full HCI on Cisco UCS running Nutanix software is the right path when you have a greenfield environment with no existing storage investment. If there is no Pure FlashArray or other external SAN under active support, starting with full HCI delivers the cleanest architecture. No external storage to integrate, no NVMe-oF fabric to design, no separate storage management relationship. One platform covers everything.

Organizations migrating from vSAN find full HCI particularly natural. VMware vSAN and Nutanix HCI are architecturally analogous. Both hyperconverge storage into the compute node. The operational model is familiar and the scaling logic is similar. Nutanix HCI is the natural landing for vSAN migrations.

For organizations where procurement complexity matters, full HCI is simpler. It represents one procurement conversation: Cisco UCS nodes running Nutanix software, single support relationship for the hyperconverged layer. Disaggregated requires separate UCS, Pure, and Nutanix contracts.

Workload profile also drives the decision. For file servers, web and app tiers, dev/test environments, and virtual desktop infrastructure, Nutanix DSF with inline dedup and compression provides excellent performance. The case for dedicated external storage is strongest for Tier-1 databases with strict IOPS and latency requirements.

Cisco UCS nodes (X-Series or C-Series) with local NVMe drives contributing to the Nutanix DSF storage pool. Standard 10GbE or 25GbE Ethernet fabric, no dedicated storage VLAN required. Replication Factor 2 requires a minimum of 3 nodes. Replication Factor 3 requires a minimum of 5 nodes. These are hard minimums, not recommendations.

Disaggregated compute-only Nutanix AHV on Cisco UCS with Pure FlashArray as external storage is the right path when you have an active Pure FlashArray investment under support. This is the dominant reason organizations choose disaggregated. If there is significant Pure FlashArray capital under an active support contract with two or more years remaining, replacing it to achieve full HCI convergence is a cost the business will not support, and should not.

Compute-only Nutanix nodes running AHV connecting to the existing FlashArray via NVMe-oF exits VMware licensing without discarding working storage infrastructure. The FlashStack with Nutanix architecture, jointly validated by Cisco, Pure, and Nutanix, formalizes exactly this path.

For Tier-1 workloads with strict performance requirements, Pure FlashArray delivers consistent, predictable all-flash performance that is not dependent on what the compute nodes are doing. For Oracle RAC, SQL Server with high IOPS requirements, or financial workloads where storage latency consistency is critical, dedicated external storage provides a higher-assurance option than distributed software-defined storage.

Disaggregated architecture also fits environments where compute and storage scale at different rates. In full HCI, adding a node adds both compute and storage capacity together. If an environment adds virtual machines frequently but storage capacity grows slowly, each node adds storage that is not needed. Disaggregated allows UCS compute nodes to be added independently of Pure capacity, and Pure capacity to be expanded independently of compute.

Cisco UCS compute-only nodes (C220 or C240 rack servers, or UCS X-Series modular) with minimal local storage. M.2 NVMe for operating system boot only, no storage drives. UCS Fabric Interconnects connect to Arista leaf switches. A dedicated NVMe-oF VLAN carries all storage traffic between UCS hosts and Pure FlashArray target ports. iSCSI connectivity to Pure is also supported for existing environments where NVMe-oF has not yet been deployed.

Some environments have a third option: mixed clusters where some workloads run on full HCI nodes and others run on compute-only nodes connecting to Pure. Nutanix supports this model within the same Prism Central management domain.

IVI generally recommends against mixed cluster types unless there is a clear workload segmentation rationale. The operational complexity of two cluster types, two storage architectures, and separate scaling models increases meaningfully without a proportional benefit in most environments. The more common path is to choose one architecture for the primary workload profile and use the other only when a specific workload genuinely requires it.

Storage architecture differs fundamentally between the approaches. Full HCI uses Nutanix DSF, a distributed software-defined fabric where every node contributes capacity. Disaggregated uses Pure FlashArray as centralized external all-flash storage. DSF is integrated with Nutanix management. Pure FlashArray is a separate platform with its own management, monitoring, and support relationship.

Scaling models operate differently. Full HCI scales out by adding nodes, which adds compute and storage simultaneously. Disaggregated scales compute and storage independently. Full HCI requires a minimum of 3 nodes for RF2 production and 5 nodes for RF3 high availability. Disaggregated requires a minimum of 3 compute nodes with no dependency on node count for storage.

Performance characteristics vary by architecture. Full HCI performance depends on node specification, local drive type and count, and cluster load. Disaggregated performance is determined by Pure FlashArray, which delivers consistent all-flash performance independent of compute activity.

Management complexity differs significantly. Full HCI is managed through Prism Central as a single unified plane. Disaggregated involves Prism Central, Pure1, and Cisco Intersight. IVI Aegis provides a unified operational view across all three via LogicMonitor.

Network requirements are simpler for full HCI, requiring standard 10GbE or 25GbE Ethernet with no dedicated storage VLAN. Disaggregated requires a dedicated NVMe-oF VLAN with jumbo frames at MTU 9000 configured end-to-end.

Full HCI cost inputs include Cisco UCS nodes with Nutanix software license and Nutanix support contract covering hardware and software. No external storage purchase is required. Disaggregated cost inputs include Cisco UCS compute hardware and support contract, Pure FlashArray hardware if purchasing new or existing investment if retaining existing Pure under active support, Pure Evergreen support subscription, Nutanix software license for compute nodes, and incremental Arista fabric cost for the dedicated NVMe-oF storage VLAN.

Key TCO variables include data reduction ratio on Pure FlashArray, which directly affects effective cost per gigabyte, and independent scaling value. Organizations should quantify how frequently compute and storage have historically needed to scale separately in their environment. Disaggregated has slightly more operational overhead given three management planes, but under Aegis, IVI absorbs this overhead as part of the co-managed services engagement.

Four questions determine your architectural path. Question one: Do you have Pure FlashArray under active support with two or more years remaining? If yes, disaggregated is almost certainly the right path. Model the cost of early Pure retirement versus retaining it under the Nutanix architecture. If no, move to question two.

Question two: Do your most demanding workloads require consistent, predictable storage performance such as Oracle, SQL Server, or financial applications with strict IOPS or latency SLAs? If yes, disaggregated with Pure FlashArray provides higher assurance. If no, full HCI performs well for general-purpose workloads and simplifies the architecture.

Question three: Do you anticipate needing to scale compute and storage at meaningfully different rates over the next three years? If compute grows faster than storage, or storage capacity is the constraint while compute is stable, disaggregated independent scaling is a financial advantage. If both grow roughly in proportion, full HCI scale-out is simpler.

Question four: How much does operational simplicity matter relative to purpose-built flexibility? If the team needs one tool and one vendor relationship, full HCI is the answer. If purpose-built components at each layer are acceptable, especially with Aegis co-managing the operational surface, disaggregated delivers more flexibility.

Full HCI is the right fit for organizations with no existing external storage investment to protect, teams migrating from vSAN who want an operationally equivalent architecture, organizations that prioritize a single vendor and single management plane, and environments where general-purpose workloads dominate and dedicated storage performance is not a critical requirement.

Disaggregated is the right fit for organizations protecting an active Pure FlashArray investment, Tier-1 database and financial workloads with strict storage performance requirements, environments where compute and storage growth rates are meaningfully asymmetric, and existing FlashStack customers who want the lowest-risk path to VMware exit without replacing hardware.

Neither path is the right fit for organizations with deep VMware NSX-T dependency that has not been addressed separately. Hypervisor migration and network virtualization migration are distinct workstreams regardless of which architecture is chosen. Neither path is right for organizations seeking fully outsourced IT with application-level support included. Both paths are co-managed infrastructure where IVI owns the platform layer and the client owns what runs on it.