The main differences between COS Lite and COS HA from data perspective are that COS HA uses different charms for the logs and metrics backends. For metrics, Prometheus is replaced with Mimir. For logs, monolithic Loki is replaced with Loki HA.
Migrating data from Prometheus to Mimir or from one charm revision of Loki to another is complex and nuanced. At this point, we recommend a retention-based phase-out.
Migration via retention-based phase-out
Deploy COS (HA) next to COS Lite, relating the new COS charms to the same applications COS Lite is related to. When the retention period elapses, switch to using the new COS deployment.