I made a mistake, which was difficult to correct. In some 24.3. version casting to my Nest Hub broke. It just did not cast any more. The quick correction was to downgrade to earlier 24.3. Then everything worked fine again. Case closed.
Later I found that this caused major effects in 24.4. versions. Recorder stopped working, all recent history graphs disappeared, and energy dashboard disappeared also. Unfortunately I had no clue of what was happening. My system log was filling with errors, which did not give any direct information where they came from.
The errors were caused by a database migration done in some 24.3. version, but probably overwritten by downgrade. Possibly later upgrades assumed that the database migrations were done already - and they were never redone (this is my theory now). Then, my Recorder database (MariaDb) was totally messed up.
I corrected this by removing MariaDb addon and adding it again. I lost maybe a week recent data, but fortunately I collect everything to VictoriaMetrics for history.
My learning is that do not downgrade, it could have strange and difficult to debug consequences.
I’m a big advocate of testing my backup and recovery processes and procedures BEFORE I need them. I know my system is unique and I need to completely understand how I can recover from any issue or disaster.
I have proven to myself that I can recover without any issues. I recommend that everyone do the same.
Good reminders. There are occasional updates to the database design, and that needs to be taken into consideration in your backup/recovery plans.
Personally, I take a copy of the entire config directory prior to any update, in addition to the normal HA backup. If I had to restore to an earlier version, I would have a good copy of the database and any configurations which I or the update may have changed as part of the update process. I also don’t depend on the HA database for any long-term data storage, so I don’t lose much if I have to delete it and have HA create a new one.
Downgrade is OK but you must be aware that database may need to be deleted before starting.
Config will throw error if there was breaking change between version but this can be corrected.
Database will just break. Deleting it should make all OK again I believe.