The goal is to make fine-tuned LLMs from a production (prod) Databricks workspace available for testing in a development (dev) workspace, leveraging Unity Catalog and MLflow, while ensuring cost-effectiveness and security. Let’s analyze the options.

Option A: Use an external model registry which can be accessed from all workspaces

An external registry adds cost (e.g., hosting fees) and complexity (e.g., integration, security configurations) outside Databricks’ native ecosystem, reducing security compared to Unity Catalog’s governance.

Databricks Reference:"Unity Catalog provides a centralized, secure model registry within Databricks"("Unity Catalog Documentation," 2023).

Option B: Setup a script to export the model from prod and import it to dev

Export/import scripts require manual effort, storage for model artifacts, and repeated execution, increasing operational cost and risk (e.g., version mismatches, unsecured transfers). It’s less efficient than a native solution.

Databricks Reference: Manual processes are discouraged when Unity Catalog offers built-in sharing:"Avoid redundant workflows with Unity Catalog’s cross-workspace access"("MLflow with Unity Catalog").

Option C: Setup a duplicate training pipeline in dev, so that an identical model is available in dev

Duplicating the training pipeline doubles compute and storage costs, as it retrains the model from scratch. It’s neither cost-effective nor necessary when the prod model can be reused securely.

Databricks Reference:"Re-running training is resource-intensive; leverage existing models where possible"("Generative AI Engineer Guide").

Option D: Use MLflow to log the model directly into Unity Catalog, and enable READ access in the dev workspace to the model

Unity Catalog, integrated with MLflow, allows models logged in prod to be centrally managed and accessed across workspaces with fine-grained permissions (e.g., READ for dev). This is cost-effective (no extra infrastructure or retraining) and secure (governed by Databricks’ access controls).

Databricks Reference:"Log models to Unity Catalog via MLflow, then grant access to other workspaces securely"("MLflow Model Registry with Unity Catalog," 2023).

Conclusion: Option D leverages Databricks’ native tools (MLflow and Unity Catalog) for a seamless, cost-effective, and secure solution, avoiding external systems, manual scripts, or redundant training.