An online backup is a backup that is still accessible to the computer which initiated the backup process. For example, if you back up all your data from your personal computer to an external hard drive that remains attached to your personal computer at all times, it is, in the sense that it exists on two physical mediums, backed up.
That data backup, however, is considered online and is susceptible to a wide range of hazards, including accidental deletion, vulnerability to viruses and malicious software, and is susceptible to power surges and other physical hazards that could damage the host computer. As such, online backups are regarded by the majority of data security experts to be merely local redundancy and not a true backup.
- By Jason Fitzpatrick on 11/1/13