An Oracle database can be configured to multiplex the redo logs, archive the redo logs, do both, or do neither. Each customer must understand their business requirements in order to determine which option or set of options is most appropriate for their solution.
A database that does not multiplex or archive the redo logs requires less administration than other options, but the database can only be recovered to the last full backup and available subsequent incremental backups if the drives that house the logs fail. If your implementation allows for little or no data loss, this is not the appropriate option.
Multiplexing the redo logs provides one or more additional copies of the logs, ideally on separate disks. Archived redo logs are those that are copied to a separate location after a log switch has occurred. Both options eliminate a single point of redo log failure, but require additional administration. In the case of archived redo logs, the archived copies must be managed regularly to prevent the disk from running out of space.