As you mention on this link (Percona XtraBackup Overview - MariaDB Knowledge Base) , xtrabackup is not supported on MariaDB 10.3 and up. By “not supported” it means that the backup will likely fail and you should use mariabackup instead.
For previous versions there are a few gotchas to consider, but was still supported.
In latter versions (let’s say 10.3 and newer), MariaDB has been diverging from upstream MySQL considerably, so not only it’s no longer a drop in replacement (moving from MySQL to MariaDB might be easy, but migrating back might not).
So as a conclusion, because of the incompatible changes and difference on internals, xtrabackup is not longer compatible with MariaDB changes in newer versions.
Thanks CTutte, appreciate link and confirmation…understand the divergence issues are present.
“likely fail” – I’d like to dig into this. Failure Modes? (outright crash, corruption, warnings flagged?) and possible workarounds. Is the forum a place to trawl for that information?
Meanwhile “mariabackup” community (or Enterprise) edition.
Let me re phrase.
Internal structues have changed, i.e undo logs, redo logs, etc…
What xtrabackups checks and assumes for MySQL/Percona Server, might not be correct for MariaDB, so the backup might fail with an error message or backup might show as succesfful but the backup might still fail when trying to restore. Under some simple/small scenarios xtrabackup might still work, but as the data set grows or the version changes it might not.
As previously mentioned, xtrabackup is compatible with upstream MySQL and Percona Server, but changes on MariaDB might (and are not) compatible with MySQL to be a drop in replacement.
Above said, you when using MariaDB version 10.3 and above you should NOT use xtrabackup but use mariabackup instead.