Hi from Australia.

a) frm file record the table structure and are only changed on `alter table` and the like.
b) ibd files are updated as innodb applies the redo log which my be a significant time after the transaction took place.

An the most important thing, don't use rsync for backups of database. To backup the database you need to get a complete copy at a single point in time. As such the only time rsync is a sufficient backup if, mariadb is shut down, or mariadb is halted by the operating system (kill -STOP).

Use backups like mariabackup, mariadb-dump. I've even seen some success filesystem snapshots if the filesystem supports this and copy from them.

If you're looking for an indicator if a transaction as been written, a changed GTID (if binary logs are enabled, good for a point-in-time recovery), or for innodb specificly, a lsn status variable.

So the RTFM link requested is https://mariadb.com/kb/en/backup-and-restore-overview/

Please take care of your backups.

And the last important thing. Test a recovery from your backup.

Thanks for using MariaDB. Suggested locations for questions however are listed on https://mariadb.com/kb/en/getting-help-with-mariadb/.

Not a bug as requested.

Hello again.

Many, many thanks for your valuable answers!

Long story short: I use rsync when databases are "cold" (MariaDB is stopped) or when a "live" backup (OpenVZ 7) is performed (CRIU saves memory/processes/etc).

But today, when restoring some backups (testing), only rsync with checksum option (reading all files and comparing data) updated *.ibd files (same time, same size).

Sorry to be "dumb" again but, could you tell me when *.ibd files stats are really updated? (filesystem => mtime)

Does "innodb_flush_log_at_trx_commit" have any impact?

As requested previously, I will be very happy (again) if you send me a "RTFM" page! ^^

If the question is really obvious, I'm really sorry to waste your time (please tell me).

Good evening from France to Australia!

You're not being dumb, please use one of the suggested locations for questions however are listed on https://mariadb.com/kb/en/getting-help-with-mariadb/. I will notice when its there, I've just got a few other things to do. Its also unclear what the significance of your today restore testing is.