Disk space high
Filesystem usage at or above the configured threshold (default 85%). At 100% services that write to this filesystem will fail; at >=95% the buffer is hours-not-days.
Remediation
When this rule fires on one of your servers, the dashboard alert detail page renders the full remediation guidance: the command to run, what to verify after, and Furnace's annotation for your specific distro + hardware. Sign in at app.glassmkr.com to see the live alert.