I have been experiencing sporadic data loss on a specific ARIA database. I have multiple ARIA databases on the same server, however programs that maintain this specific DB does not use any transactions or LOCK TABLE commands.
Please also note that I use an encryption plugin (using the template for file-based encryption plugins from the MariaDB website), however I do not believe there is a problem with the plugin itself, since none of the other ARIA DBs on the same system are affected.
The symptoms are as follows:
Log data to some tables in an ARIA DB table (with ARIA encryption plugin enabled) at a reasonable speed (I went with 5 inserts a second - make sure you don't do transactions or LOCK TABLES commands) and then force close the virtual machine (to emulate a power outage).
Then power the virtual machine back up and check the database tables to see if the tables have been recovered and to see if there is any data loss/resetting of Ids (similar to what you expect from a TRUNCATE TABLE command, except for all tables in the DB).
On my development system I found that all tables in the specific database had all data removed (blank tables) and all auto_increment Id (primary) fields had been reset to zero (as if no data had ever been written to the table).
Please note that ALL tables are being wiped within this DB, not just the specific table being written to. No other ARIA DBs seem to be affected (possibly because programs use LOCK TABLES to these DBs).
Final note: I have not been able to reproduce this in my test lab, since when I try to emulate the power outage (crash recovery) the table being written to actually becomes unrecoverable (even running the commands to manually repair does not work).