>> If files are assumed to >> be sound, pg_rewind will adjust the old master as a new standby
To use pg_rewind, we should either enable wal_log_hints or initialize data directory with checksum enabled. These are not default and will not be enabled in most of the cases. In those scenarios, we cannot pg_rewind to sync data.
>> The .partial file is created when timeline diverges at midst of a WAL segment
I read somewhere that a .partial file will definitely be created during promotion of the slave database and is introduced from the postgres 9.5 version. Please correct me if I am wrong. But in my scenario, it is not getting generated.