Build Custom Dashboard - Multiple LAWs Across Multiple Azure Subscriptions

Hello Taranjeet Malik

Thank you for posting your query on Microsoft Q&A platform.

You have VMs spread across multiple subscriptions and multiple Log Analytics Workspaces (LAWs), and you want to build a single dashboard that shows VM CPU, Memory, Disk, and Heartbeat data.

To check whether a VM is connected to a Log Analytics Workspace (LAW), and which LAW it is connected is Azure Monitor Agent (AMA) and Data Collection Rules (DCRs).

The AMA controls data flow, and the workspace destination is defined inside the DCR, not in the VM’s diagnostic settings, which is why your diagnostic blade looks empty as Azure Diagnostics Extension is being deprecated.

To verify which LAW a VM is reporting to follow the below steps:

Go to Azure Monitor → Data Collection Rules → Select the DCR → Destinations tab.

This shows the exact LAW(s) the VM is sending logs/perf counters to.

To Cross‑check using Log Analytics (KQL) run the below query inside each workspace:

Heartbeat
| summarize by Computer, _ResourceId

If the VM appears here, it is reporting to this workspace.

If VMs are not reporting to a LAW You are correct that without sending data to a LAW, you cannot use KQL to query CPU, Memory, Disk, or Heartbeat, because those tables are created only when a VM sends data via AMA:

• Perf
• InsightsMetrics
• Heartbeat

Without these tables, no unified dashboard can be built.

Below are the Supported alternatives if VMs are not connected to LAW:

1. Use Azure Monitor Metrics (Platform Metrics): Azure still gives you host‑level metrics even without LAW:

• CPU (host level)
• Disk IO (host level)
• Network metrics

But guest OS metrics such as memory, disk usage, heartbeat are not available.

Reference: https://dori-uw-1.kuma-moon.com/en-us/azure/azure-monitor/visualize/tutorial-logs-dashboards

2. Use VM Insights (Recommended for multi‑subscription dashboards): VM Insights automatically aggregates Guest CPU, Guest Memory, Guest Disk usage, Heartbeat, Dependency maps (optional).

Requirement is AMA + DCR + LAW

Reference: https://dori-uw-1.kuma-moon.com/en-us/azure/azure-monitor/vm/vminsights-enable?tabs=portal

3. Use Azure Workbooks which supports multiple LAWs in one dashboard: You can query multiple workspaces in a single query.

union workspace("<LAW1-ID>").Heartbeat,
      workspace("<LAW2-ID>").Heartbeat

Reference: https://dori-uw-1.kuma-moon.com/en-us/azure/azure-monitor/logs/cross-workspace-query

Since you have Multiple subscriptions, Multiple LAWs, Need cross‑environment VM health reporting the correct and supported solution is:

Use Azure Monitor Agent (AMA) + DCRs + VM Insights + a single Workbook which gives Centralized dashboard, Multi‑LAW queries, Full guest OS metrics, Unified heartbeat, Scalable multi‑subscription design.

If you have any other queries, please do let us know.

Thanks,

Suchitra.