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CSA Loom — the Microsoft Fabric experience for Azure tenants where Fabric isn't yet available: lakehouses, warehouses, notebooks, semantic models, Activator rules, Data Agents, across Commercial, GCC, GCC-High, and DoD IL5

Tutorial 08 — Forward-migrate a lakehouse to Fabric

When Microsoft Fabric reaches your audit boundary, migrate your Loom lakehouse forward via OneLake shortcut. 30 minutes (demo only — real migrations span weeks).

Prerequisites

  • Loom lakehouse with Bronze / Silver / Gold tables (from previous tutorials)
  • Fabric workspace in the same Entra tenant with F-SKU capacity
  • fiab-migrate CLI (ships in v1.1; this tutorial uses Loom v1.1+)

Important: this is the strategic anchor

The whole reason CSA Loom is a defensible investment is that this migration works cleanly. You're testing the bridge today against a Fabric Commercial workspace so you understand the pattern before your Gov boundary's Fabric GA arrives.

Steps

1. Verify Fabric workspace is ready

Open Fabric portal at https://app.fabric.microsoft.com (Commercial) or https://app.fabric.microsoft.us (Gov, when Fabric Gov GAs): - Workspace exists - Bound to F-SKU capacity (F8+) - You're a Workspace Admin

2. Snapshot the Loom estate

fiab-migrate snapshot \
  --admin-plane-sub-id <YOUR-SUB-A> \
  --workspace <your-loom-workspace> \
  --output ./loom-snapshot.json

Output captures: - Workspace definition - All lakehouses + tables (metadata, not data) - Semantic models (TMDL) - Activator rules (JSON) - Data Agent configs (JSON) - Lineage from Purview

3. Plan migration

fiab-migrate plan \
  --snapshot ./loom-snapshot.json \
  --target-fabric-tenant <TENANT-ID> \
  --target-workspace <fabric-workspace-id> \
  --output ./migration-plan.json

Plan output: - Per-item verdict (Direct / Manual / Skip) - Dependency order - Estimated effort per item

For this tutorial, the lakehouse should show as Direct (OneLake shortcut).

4. Execute: create OneLake shortcut

fiab-migrate execute \
  --plan ./migration-plan.json \
  --workload lakehouse \
  --commit

This: - Creates a Fabric Lakehouse item in the target workspace - Creates a OneLake shortcut from Tables/ pointing at your Loom ADLS Gen2 path: https://onelake.dfs.fabric.microsoft.com/<workspace>/<lakehouse>/Tables/noaa_silver_daily → abfss://<container>@<storage>.dfs.core.windows.net/Tables/noaa_silver_daily - Zero data movement — Fabric reads the Delta directly via the shortcut

5. Verify in Fabric

Open the Fabric Lakehouse: - noaa_silver_daily appears in Tables (shortcut icon) - Query in Fabric notebook: 

df = spark.table("workspace_name.lakehouse_name.noaa_silver_daily")
df.show(10)
- SQL Analytics Endpoint can read the same table

Compare to Loom: query returns identical results.

6. Migrate semantic model

fiab-migrate execute \
  --plan ./migration-plan.json \
  --workload semantic-model \
  --commit

This: - Re-authors the TMDL semantic model with Direct Lake on OneLake storage mode (replaces the Direct-Lake-Shim warm-cache pattern) - Deploys to Fabric workspace - Power BI reports automatically rebind if they used the same semantic model name

7. Compare freshness

In Loom: - Direct-Lake-Shim refresh latency: 5-30 s (per Tutorial 03)

In Fabric (after migration): - Direct Lake on OneLake native: sub-second

This is the gap that closes when you forward-migrate.

8. Side-by-side run

Don't decommission Loom immediately. Run side-by-side for 30-90 days: - Loom continues to serve queries - Fabric serves queries via OneLake shortcut (same data, faster freshness) - Compare results, validate identity passthrough works in both - Migrate Power BI reports to Fabric workspace per cadence

9. Decommission (when ready)

After parallel-run validation: - Stop Direct-Lake-Shim service (Fabric handles freshness natively) - Update Console UI to flag the workspace as "migrated to Fabric" - Optionally retire the entire Loom workspace if all artifacts migrated - ADLS Gen2 data remains (now accessed via OneLake shortcut from Fabric)

What's next

Cleanup (this tutorial)

If just demoing: - Delete the Fabric Lakehouse shortcut (Fabric portal → Settings → Delete) - Loom estate untouched

Troubleshooting

  • OneLake shortcut creation fails: verify Entra B2B trust between Loom Gov tenant + Fabric Commercial tenant (only relevant for cross-cloud hybrid; same-tenant works natively)
  • Query result mismatch: verify schema parity (Fabric reads same Delta files, so should be identical)