Controlled Shutdown and Fast Check Features

Controlled Shutdown and Fast Check Features

Summary

This Knowledgebase article explains the Fast Check feature introduced in Neverfail Heartbeat v6.5, and how it works in conjunction with the Controlled Shutdown feature to maintain synchronization, particularly in environments with large datasets or WAN links with limited bandwidth.

Fast Check & Controlled Shutdown: Working Together

The Fast Check feature is an enhancement to the standard Full System Check, designed to drastically reduce verification times on server reboot — but only if the server was previously shut down using Neverfail’s Controlled Shutdown mechanism.

Controlled Shutdown is a Neverfail feature that intercepts Windows OS shutdown or reboot commands and coordinates a graceful shutdown of protected services. For Neverfail to take control of a shutdown event, you must configure the Controlled Shutdown schedule in the Neverfail GUI (see screenshot below). Only shutdowns or reboots occurring within the defined time intervals (highlighted in blue on the calendar) are intercepted.


When a Controlled Shutdown is triggered, Neverfail performs the following sequence:

  1. Graceful stop of Protected Applications: Neverfail stops all protected services, allowing them to flush in-memory data to disk.

  2. Real-time replication of final changes: All resulting file and registry changes are replicated to the Passive server before replication is stopped.

  3. Shutdown markers written to registry: Neverfail writes internal flags indicating replication completed successfully and the shutdown was controlled while replication was stopped in Full Sync.

  4. Safe OS shutdown: Finally, Neverfail stops its own service and hands control back to the OS to complete the reboot or shutdown.

Upon restart, Neverfail reads the registry markers and understands that the previous shutdown was controlled and replication stopped in-sync. It will then initiate a Fast Check — a lightweight verification process that typically takes less than 60 seconds. 

During Fast Check:

  • Protected Applications remain stopped temporarily.

  • File and registry integrity is compared to ensure both servers remain in perfect sync.

  • If successful, Neverfail resumes replication and starts Protected Applications—without requiring a time-consuming Full System Check.

Why It Matters

This approach is especially beneficial when:
  • Replication occurs over slow or congested WAN links, or

  • The system handles large volumes of data, making Full Sync costly in time and bandwidth.

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