docs: backup restore - add warning to not backup DB_DATA_LOCATION (im…

…mich-app#9353)

backup restore add warning for backing up folder

docs/docs/administration/backup-and-restore.md

@@ -17,6 +17,10 @@ Refer to the official [postgres documentation](https://www.postgresql.org/docs/c
 
 The recommended way to backup and restore the Immich database is to use the `pg_dumpall` command. When restoring, you need to delete the `DB_DATA_LOCATION` folder (if it exists) to reset the database.
 
+:::caution
+It is not recommended to directly backup the `DB_DATA_LOCATION` folder. Doing so while the database is running can lead to a corrupted backup that cannot be restored.
+:::
+
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