Technology

Microsoft OneLake

The single, tenant-wide data lake under Microsoft Fabric, built on ADLS Gen2, storing tables as Delta by default and exposing them through an Iceberg REST Catalog API for external engines.

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Summary

What it is

The single, tenant-wide data lake under Microsoft Fabric, built on ADLS Gen2, storing tables as Delta by default and exposing them through an Iceberg REST Catalog API for external engines.

Where it fits

Microsoft's "OneDrive for data" — the shared lake every Fabric workload addresses, with open-catalog APIs (Iceberg REST + Unity Catalog Open APIs) so Snowflake, Dremio, Trino, and Databricks reach Fabric data without an export step.

Misconceptions / Traps

OneLake is Azure/ADLS-backed, not literally S3 — it participates in the open lakehouse via the Iceberg REST Catalog standard, not via being S3-compatible storage.
"Bidirectional with Snowflake" means shared Iceberg metadata over one physical copy, not two-way replication.

Key Connections

implements Iceberg REST Catalog Spec — IRC endpoint for external-engine access
enables Apache Iceberg — Fabric tables surfaced as Iceberg
alternative_to Amazon S3 Tables — the Azure-side managed-table-storage analogue
solves Vendor Lock-In — open-catalog access for Fabric-resident data

Definition

What it is

The single, tenant-wide data lake underneath Microsoft Fabric — one logical OneLake per tenant, built on Azure Data Lake Storage Gen2, that every Fabric workload (Lakehouse, Warehouse, Power BI, Real-Time Intelligence) reads and writes. Tables are stored as Delta Lake by default and exposed through an **Iceberg REST Catalog (IRC) API** for external engines.

Why it exists

Microsoft's answer to data-copy sprawl. Instead of each analytics product holding its own copy of the data, OneLake is a shared "OneDrive for data" that all Fabric engines address directly. The open-catalog surface (Iceberg REST + Unity Catalog Open APIs) is the interoperability bet — Fabric data should be reachable by Snowflake, Dremio, Trino, and Databricks without an export step.

Primary use cases

Tenant-wide lake for Microsoft Fabric workloads, cross-engine access to Fabric tables via the Iceberg REST Catalog API, Snowflake↔OneLake bidirectional Iceberg interop, Azure-side lakehouse storage that participates in the open table-format ecosystem.

Recent developments

Latest signals

OneLake exposes an Iceberg REST Catalog (IRC) API endpoint for external engines. External engines — Snowflake, Dremio, Trino — query Microsoft Fabric tables using standard Iceberg catalog connection strings, with no export step. Per Microsoft Fabric — access your Fabric tables in Apache Iceberg format.
Snowflake ↔ OneLake bidirectional interoperability is GA. OneLake can natively store Snowflake-managed Iceberg tables, and Fabric data is auto-converted to Iceberg for direct Snowflake access — read and write across both platforms over one physical copy. Per Microsoft — OneLake and Snowflake interoperability is now generally available.
OneLake is adding open-catalog APIs (Iceberg REST + Unity Catalog Open APIs). The roadmap makes OneLake's structured and unstructured data natively reachable by the broader open lakehouse — including Databricks, which is adding support to surface all OneLake data in Unity Catalog. Per Databricks — Expanding support for OneLake in Unity Catalog.