OneLake
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Category: Integration & Analytics
Summary: Fabric's single, unified, tenant-wide data lake storing all workloads' data in Delta format.
Overview
OneLake is Microsoft Fabric's single, unified, tenant-wide data lake (built on Azure Data Lake Storage Gen2) that automatically stores data for every Fabric workload in one open, shareable location — eliminating the need for teams to copy or duplicate data across separate lakes. When Azure Cosmos DB Mirroring for Fabric is enabled, mirrored data lands directly in OneLake in Delta format, immediately available to Spark notebooks, Direct Lake-mode Power BI reports, and other Fabric experiences without additional data movement.
More Info & Links
DP-420 Style Practice Questions
Q1. What is OneLake in Microsoft Fabric?
- A. A single, unified, tenant-wide data lake shared across all Fabric workloads
- B. A per-workspace cache used only by Power BI
- C. A dedicated backup store for Azure Cosmos DB
- D. A replacement for Azure Cosmos DB's transactional store
Q2. In what format does Azure Cosmos DB Mirroring for Fabric store data once it lands in OneLake?
- A. Delta format
- B. Raw JSON documents only
- C. A proprietary binary Cosmos DB format
- D. CSV files
Answer Key
Answers are listed at the very end so you can attempt the questions first.
- Q1 (OneLake): A. A single, unified, tenant-wide data lake shared across all Fabric workloads — OneLake is Fabric's single logical data lake for the entire tenant, shared automatically across workloads.
- Q2 (OneLake): A. Delta format — Mirrored data is stored in OneLake as open Delta format tables, making it directly queryable by Fabric engines.
DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page
