Introduction: When HCI seems beneficial, and when it doesn't
HCI integrates compute, storage, networking, and virtualization into a single, software-defined system, often simplifying management and accelerating deployment. This makes it attractive for Virtual Desktop Infrastructure (VDI), remote offices, and disaster recovery tasks. While initial HCI investments might be higher, it often promises a lower Total Cost of Ownership (TCO) over 3–5 years due to reduced operational expenses 1.
However, there are scenarios where a classic three-tier architecture, consisting of separate servers, Storage Area Networks (SAN)/Network-Attached Storage (NAS), and networking equipment, can prove more cost-effective. This applies, for example, to large databases or high-performance computing, where a high degree of control and independent resource scaling are required. The choice between HCI and classic architecture demands a deep analysis of an organization's needs, growth plans, and existing IT environment.
Scaling: Linear growth versus granularity
A key difference between HCI and classic architecture lies in the scaling model. HCI scales by adding nodes that include both compute resources (CPU, memory) and storage. This simplifies expansion following a "pay-as-you-grow" model. However, this linear model can become inefficient if the need for compute and storage grows asymmetrically. For example, if an organization requires significantly more compute power but only a slight increase in storage capacity, or vice versa, adding a full HCI node will result in redundant and unused resources, increasing costs.
Classic architecture allows for independent scaling of each layer: adding servers for compute or disk arrays for storage. This provides granularity and flexibility, allowing for precise alignment with workload needs. For high-performance databases or specialized applications demanding maximum storage performance, separate SAN solutions can offer better efficiency and lower latency than distributed HCI storage. In such cases, despite initial complexity, the classic approach might prove more cost-effective in the long run by avoiding "stranded" capacity. Some modern HCI solutions, such as dHCI (disaggregated HCI), attempt to address this issue by allowing independent scaling of compute and storage 2.
Licensing: Hidden costs and vendor lock-in
Licensing models are one of the most complex aspects when comparing the cost of HCI and classic architectures. HCI vendors often license their solutions based on the number of physical CPU cores or nodes. For example, Nutanix Cloud Infrastructure (NCI) is licensed per physical CPU core 3. VMware vSphere Foundation (VVF) and VMware Cloud Foundation (VCF) from Broadcom also use per-core licensing, often with a minimum of 16 cores per CPU 4, which can significantly increase costs if processors with fewer cores are used.
In a classic architecture, licensing for operating systems, hypervisors, and storage software can be more fragmented, but this also allows for cost optimization by choosing solutions from different vendors. If an organization already has existing licenses for classic infrastructure components that can be transferred, this can significantly reduce initial investments. With a large number of cores in servers, per-core HCI licensing can quickly become more expensive than the combined licenses for separate classic architecture components, especially if these components do not require constant upgrades to the latest versions.
Storage overhead: Efficiency versus redundancy
In HCI, storage overhead is a significant factor impacting overall cost. To ensure fault tolerance and high availability, HCI systems use replication mechanisms (e.g., Replication Factor in Nutanix) or erasure coding, which require additional disk space. For instance, to protect against two simultaneous node failures, a minimum of 5 nodes and RF3 replication (three synchronous copies of data) might be needed, reducing usable capacity to approximately 33% of the total raw capacity 5. Furthermore, some HCI solutions require reserving a portion of resources on each server to ensure recovery after failures, further reducing available capacity.
In classic SAN/NAS solutions, disk space utilization efficiency can be higher because data protection mechanisms (RAID, snapshots) can be more flexibly configured and optimized for specific needs. While SAN also has its own overheads, they can be better controlled and adapted to workload requirements, especially for large data volumes where every terabyte matters. For environments with high demands for raw storage capacity without significant compute needs, HCI storage overhead can make it less cost-effective.
Support and operational costs: Simplification or complication?
One of the main advantages of HCI is simplified management and support due to a unified platform and centralized interface. This can lead to lower operational costs and reduced burden on IT staff. HCI vendors often offer a single point of contact for both hardware and software support, streamlining problem resolution.
However, in certain scenarios, integrated HCI support can be more expensive or less flexible. If an organization already has qualified personnel to support individual components of a classic architecture (e.g., SAN, network, and virtualization specialists), transitioning to HCI may require retraining or hiring new specialists, increasing costs. Additionally, for large and complex environments requiring deep expertise in each individual layer, a single point of support might be less effective than direct contact with experts for specific hardware or software. In cases of complex issues, the integrated nature of HCI can complicate diagnosis and resolution, potentially increasing downtime and operational costs.
Pros and cons
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Practical checklist: When HCI is more expensive than classic
For a CTO facing an architectural choice, clear evaluation criteria are essential. This checklist will help identify scenarios where hyperconverged infrastructure might be more expensive than classic server architecture:
- Do you need asymmetric scaling of compute and storage? (Yes/No)
- Are there high demands for raw storage capacity without significant compute needs? (Yes/No)
- Do you have existing, transferable licenses for individual components? (Yes/No)
- Is the cost of per-core/per-socket HCI licensing high with a large number of cores? (Yes/No)
- Is there a need for specific, high-performance storage solutions that don’t integrate with HCI? (Yes/No)
- Do you have qualified personnel to support individual components of a classic architecture? (Yes/No)
- Is there a limited budget for initial investments but flexibility in future expenditures? (Yes/No)
If most answers are “Yes,” a classic architecture will likely be more cost-effective.
Softline IT assists in planning and implementing server infrastructure solutions: from auditing the current state to a coordinated change plan.
Softline IT helps teams plan and implement server infrastructure, from an assessment of the current environment to an agreed change plan.
