AZ-305
Deep Dive
The AZ-305 includes designing migrations: classifying workloads with the 6 Rs of CAF, discovering and assessing with Azure Migrate, moving databases with DMS, and choosing online vs offline for large-scale data.
Contents
| Strategy | What it involves | Signal |
|---|---|---|
| Rehost (lift-and-shift) | VM → VM with no changes. Fast, no PaaS benefits | "Migrate fast without touching code", "exit the datacenter in 6 months" |
| Refactor (repackage) | Minimal changes for PaaS: app → App Service, DB → MI, containers | "Reduce administration without rewriting" |
| Rearchitect | Redesign parts: monolith → microservices, queues, scaling | "The app doesn't scale; modernize the architecture" |
| Rebuild | Rewrite cloud-native from scratch (serverless, Container Apps) | "The legacy code isn't viable" |
| Replace | Replace with SaaS (Dynamics, Salesforce) | "Stop maintaining a custom-built app" |
| Retire | Decommission — the app adds no value; remove it from the inventory | "Inventory finds apps with no active users or duplicated by consolidation" |
CAF migration process: Assess → Migrate → Optimize → Secure & Manage, landing in an already-governed landing zone (not migrating into an empty subscription with no policies).
Discovery & Assessment
Migration
| Tool | What for |
|---|---|
| Azure Database Migration Service (DMS) | SQL Server → Azure SQL migration (DB/MI/VM): offline or ONLINE (minimal downtime with continuous sync and cutover) |
| Azure SQL Migration extension (Azure Data Studio) | Assessment + guided migration of SQL Server, with target and SKU recommendation |
| Managed Instance Link | Near real-time replication SQL Server ↔ MI — migration with minimal downtime or hybrid DR |
| Backup/restore to a URL | The simple path with a downtime window (full + logs to blob, restore at the destination) |
| Data Factory | Move/transform DATA between heterogeneous stores (doesn't migrate the engine) |
Online vs offline
"The database cannot be down for more than X minutes" → online migration (DMS online / MI Link): continuous replication + a brief cutover. If there's a wide maintenance window → offline (simpler and cheaper).
| Method | When |
|---|---|
| AzCopy / Storage Explorer | GBs to a few TBs over the network — scriptable, SAS or Entra ID credentials |
| Azure Storage Mover | Managed service for moving SMB/NFS shares and blobs to Azure — project/job with progress tracking, no manual scripts |
| Azure Data Box (physical appliance) | Insufficient bandwidth or massive data: Microsoft ships the appliance. Data Box Disk (40 TB), Data Box (80 TB), Data Box Heavy (~1 PB) |
| Data Box Gateway / Azure File Sync | CONTINUOUS hybrid transfer (virtual gateway / share caching) |
| Data Factory | Scheduled pipelines with transformation between heterogeneous stores |
| Import/Export (your own disks) | Alternative to Data Box using your own SATA disks |
Rule of thumb
Calculate the time over the network: 100 TB over 100 Mbps ≈ 100+ days. If the network transfer time is unworkable or there's no bandwidth → Data Box. If the data keeps changing, combine: bulk with Data Box + delta over the network. To move shares or blobs with no scripting → Storage Mover.
| Requirement | Design |
|---|---|
| Inventory 500 VMware VMs with no agents installed | Azure Migrate appliance (agentless discovery) |
| Know which servers make up each application | Dependency analysis |
| Size target VMs by real usage, not specs | Assessment with right-sizing |
| SQL Server → MI with minutes of downtime | DMS online / MI Link |
| Migrate an app without touching code or OS | Rehost with the Migration tool |
| .NET web app to PaaS with minimal changes | Refactor → App Service |
| App with no users after the inventory — don't migrate it | Retire (decommission) |
| 300 TB over a 200 Mbps link | Azure Data Box (80 TB) or Data Box Heavy (~1 PB) |
| Move SMB/NFS shares or blobs with no scripts | Azure Storage Mover |
| Validate the migration before cutover | Test migration into an isolated VNet |
| Sync on-prem shares with the cloud during the transition | Azure File Sync |
Did you get this topic?
Test what you just learned
A company must migrate 200 VMware VMs and 40 SQL Server instances to Azure. Before moving anything they need: a complete inventory with no agents installed, a dependency map to group servers by application, cost estimation with right-sizing, and for the most critical DBs a migration with minutes of downtime. What combination do you use?
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