Comparing on-premises and cloud RAG: processing, operations and full cost

Compare on-premises, provider-hosted and hybrid RAG by recording processing first, then comparing feasible work and costs. Local source documents do not establish local queries, embeddings, model inputs, logs or backups.

This guide addresses hosting and operating proposals. Use the component data-flow guide to inspect transfers and responsibilities in detail.

Separate location, network and processor

NIST SP 800-145, published in 2011, distinguishes cloud service and deployment models. Private cloud can be third-party operated and on or off premises. A VPC network arrangement does not independently establish non-third-party processing or control of every support, storage and transfer path.

Inspect actual services rather than assuming cloud includes everything or on-premises means complete control. Hybrid adds dependencies to evaluate; it is not automatically a superior compromise.

Attach requirements to actual data and use

Establish institution, service, data, recipients, locations and applicable rules/contracts. Sensitivity matters but does not create a universal financial/medical on-premises mandate or unconditional cloud permission.

The current FSC financial outsourcing regulation, amended April 13, 2026, sets offshore/cloud conditions for covered institutions and retains institutional oversight. Check applicable location-control, specified consumer-finance storage, exceptions and backup provisions. It rebuts a blanket ban but does not approve a particular RAG transfer or cover every financial subsector or medical institution.

For personal and medical data, establish purpose, conditions, recipients and safeguards under Taiwan's PDPA. Hosting, de-identification and certification labels do not independently authorize use. Resolve requirements with appropriate owners before choosing feasible options.

Compare full cost under the same assumptions

Fix workload, documents/queries, models, input/output sizes, index scale, concurrency, availability, retention and support. Date bids and specify currency, usage assumptions and exclusions.

Existing equipment can have opportunity and maintenance costs. Managed services retain application, data and access responsibilities. Do not assume zero setup/operations, fixed cost multipliers or accounting treatment from topology.

Substantiate schedule, performance and updates

Estimate from approved inputs, procurement/service access, integration and acceptance dependencies. Measure retrieval, model, network and queues across the whole query path rather than inferring answer latency from database location.

Agree versions, change notices, evaluation and recovery. A provider update is not automatically suitable; self-maintenance needs capacity and skill. Compare actual support conditions.

Test a bounded next decision

For a hypothetical approved-document query, use representative questions and agreed limits to assess flows, permissions, quality and failures. Evidence supports the next build or expansion decision, rather than an unsupported client cost benchmark.

Bring the selected processing scope, owners, cost assumptions and dependencies to the existing RAG knowledge-system discussion, with inspectable outputs and acceptance for the next stage.