Checksum Monitoring Detects Silent Backup Corruption

A backup directory can exist with the expected filenames while one archive is truncated or modified after creation. I ended up treating hserver_backup_checksum_ok and checksum verification age as the useful observation point rather than relying on a generic service-up indicator. Verifying the recorded manifest catches integrity failures that timestamp and file-size checks cannot reliably detect.

This is a good example of integrity monitoring. The purpose is to reduce ambiguity during an incident: a signal should tell me which layer to inspect next, not simply confirm that something somewhere looks unusual.

For production I use the following guardrail: Record the last successful checksum verification time, alert on failure, and treat unreadable evidence differently from a known-bad checksum. The same rule keeps the dashboard useful when the system grows and more targets are added.

The implementation is traceable to f10f5c7 in the hserver repository. That commit is the concrete reference for the collector, alert, dashboard, or runtime change behind this article.