This document covers the concept and usage of the consistency scan feature.
The consistency scan reads all replicas of each shard to verify data consistency at a configured rate. It is useful for finding corrupt cold data by ensuring that all data is read periodically. Any errors found will be logged as TraceEvents with Severity = 40.
You can configure the Consistency Scan via the FDB :ref:`command line interface <command-line-interface>` using the consistencyscan command.
Enable consistency scan to scan the cluster once every 28 days with a maximum speed of 5MB/s: consistencyscan on maxRate 5000000 targetInterval 2419200.
Disable consistency scan on the cluster: consistencyscan off.
View the current stats for the consistency scan: consistencyscan stats.
The consistency scan role publishes its configuration and metrics in Status JSON under the path .cluster.consistency_scan.
ConsistencyScanMetrics show the over-time stats of the consistency scan's behavior, including bytes scanned, error counts, inconsistencies found, etc...