If you wish, a log file can be maintained for each day. This is particularly useful in tracking server use.
The log files are in the industry standard W3C log file format, meaning that your log files can be interpreted by numerous third part log analysers.
A wide range of events (useful for debugging) will be logged, eg FTP, FTPS and SFTP connections, failure of SSL handshakes, incorrect SSH public key negotiation, incorrect ciphers, disconnections from blacklisted IP Addresses.
Be wary, log files can consume a great deal of disk space if allowed to accumulate!