ibdata* is a shared table space (It managed all data)
ib_logfile* seems to be a log file.
Data is not updated directory to the table space, but once the update contents are written to the log file.
After that, it seems that the flow is reflected in table space.
Tablespace updates are expensive and are not reflected immediately.
By writing to the log file, the writing performance is improved.
cd /var/lib/mysql ls sud cat ib_logfile0