Diagnostic settings vs Application Insights: where do Azure logs go?

The short version: Azure has two independent logging paths. Diagnostic settings are the platform's view — control-plane and resource logs you route to a Log Analytics workspace. Application Insights is the application's view — telemetry your app's SDK sends, which lands in its own or a linked workspace. A resource can use both, neither, or send them to different workspaces — which is why "where are my logs?" is a genuinely confusing question.

Path A — Diagnostic settings (the platform)

Every Azure resource can emit platform logs and metrics: who changed what, resource-level events, throughput. You turn these on with a diagnostic setting that routes them to a destination — usually a Log Analytics workspace, sometimes storage or Event Hubs. Nothing is captured until you create that setting. This is infrastructure telemetry, and it exists whether or not anyone wrote application code.

Path B — Application Insights (the app)

Your application sends its own telemetry — requests, dependencies, exceptions, traces — through the Application Insights SDK or auto-instrumentation. This lands in an Application Insights resource backed by a Log Analytics workspace (its own, or one you linked). This is application telemetry, and it exists because the app emits it, independent of any diagnostic setting.

The two paths side by side

Why the confusion

The two paths are unrelated. A web app might route its platform logs to workspace X via a diagnostic setting while its Application Insights telemetry lands in workspace Y. Ask "where are the logs for this app?" and the honest answer is "which logs?" — the platform's or the app's. They can even live in different workspaces owned by different teams.

How to tell where a resource's logs actually go

1. Check the resource's diagnostic settings — that tells you the platform destination (which workspace, storage or Event Hub, if any).
2. Check its Application Insights connection — that tells you where the app telemetry lands.
3. Expect them to differ. One resource can feed two workspaces; a missing diagnostic setting means platform logs simply aren't being captured.

In Calma Cloud, the Observe agent resolves this for you — it probes which workspace actually holds a resource's telemetry rather than guessing, which matters when a resource group has several Application Insights resources pointing at different workspaces.

A few common scenarios

• "I see no logs at all." Usually no diagnostic setting was ever created — platform logs aren't captured by default.
• "App Insights has data but the resource logs are empty." The app is instrumented (Path B) but no diagnostic setting routes the platform logs (Path A).
• "Logs are split across two workspaces." Normal — platform logs to one, app telemetry to another.

See how the Observe agent answers this in plain language →

FAQ

• Do diagnostic settings and Application Insights overlap? Rarely by content — one is platform logs, the other app telemetry. They can point at the same workspace but capture different things.
• Where do Application Insights logs get stored? In a Log Analytics workspace backing the Application Insights resource (workspace-based mode).
• Why do I see no logs even though the resource is running? Often because no diagnostic setting was ever created — platform logs aren't captured by default.
• Can one resource send logs to two workspaces? Yes — platform logs to one, app telemetry to another. This is common and a frequent source of confusion.
• Which one do I need? Usually both: diagnostic settings for the platform view, Application Insights for the application view.
• Does enabling diagnostic settings cost anything? The setting is free; you pay for the data ingested and retained in the destination workspace.