Hi Tpahuja,
I am not sure on which device you are trying to configure. However, I tested it on Cisco Catalyst Switch and IOU and it is working fine.
Logging messages will be sent on both locations; Syslog Server and Flash (Im using IOU so it's registered as unix I guess)
Configurations:
logging buffered 16384 7
logging host 1.1.1.1
logging persistent url unix:/syslog.txt size 16384 filesize 16384
Results: