Data redundancy is when the same data is entered multiple times it can also mean when unnecessary information is present in the database . This can lead to anomalies which are sets of data which are repeated. Backing up is a way to ensure that if data is repeated you can restore to a previous version where there are no anomalies present. Data redundancy can help prevent data loss on servers , HDDs , Operating Systems. RAID can be used to ensure backups of data is present.