Redundancy Backing up contents in /data directory

I am testing Gateway redundancy between two gateways, where the failover gateway is on the "warm" setting. The connection is good and the two gateways seem in sync except for contents of a folder in the {installPath}/data directory.

It looks like the initial sync or creation of the folder in the data directory was synced to the backup gateway, but any changes to the contents of the files (sqlite and some other things) within the directory on the primary or master gateway are not being synced back to the secondary gateway, and are not available for failover.

Does anyone have any experience keeping files in the data directory synced? Is there a better way to keep files available on the secondary in case of failover?

There's no automatic way to do it. Module developers are supposed to handle this case for any files that matter to their code.

The most reliable way to keep content available for both members of a redundant pair is to store the content outside Ignition, typically in a redundant database cluster.

(Side note: SQLite is not fit for production purposes, other than for Ignition's own light-duty configuration files and logs. It is single-threaded.)

Also, you can request a full sync when needed.