Microsoft OneLake

OneLake is the lake behind Microsoft Fabric. It is not a storage account, so there is no key, connection string or SAS URL to paste: a Microsoft sign-in is the only way in.

Ways to connect

• Sign in with Microsoft, in Settings → OneLake. The sign-in happens inside the app, in your browser, and it is the same one Azure Blob Storage uses — signing in to one signs you in to the other.
• An app registration, for a machine with no person in front of it: set AZURE_TENANT_ID, AZURE_CLIENT_ID and AZURE_CLIENT_SECRET before the app starts.
• The Azure CLI. If az is already signed in, its token is used.

You also need a Fabric workspace. Without one there is nothing to list: start a trial from the account menu at app.fabric.microsoft.com.

What lands in the tree

A workspace is a root. Your personal My workspace is not listed — OneLake does not offer it as a workspace.

Inside a workspace, every Fabric item is a folder named with its kind, and a lakehouse holds its files and its tables:

sales.Lakehouse/
  Files/
  Tables/
    dbo/
      orders/
        _delta_log/
        part-00000-….snappy.parquet

A table under Tables/ is a Delta table, so it opens and queries as one — see data lake tables.

What you can change

Fabric owns the top three levels: the workspace, the item, and the item's own folders such as Files/ and Tables/. OneLake refuses to write there, so the app refuses first, and says why. Below them, copy, move, rename and delete work as they do in any bucket — see copy, move, rename, delete.

In SQL

A OneLake path is written the way Fabric writes it:

SELECT * FROM 'abfss://sales@onelake.dfs.fabric.microsoft.com/sales.Lakehouse/Files/orders.parquet'

Cost

Fabric bills capacity, not bytes, so a OneLake row has no cost, storage class or region. The columns stay empty rather than showing a number that is wrong.

Next: MinIO.