Any backup is better than no backup at all. On closer examination, the way backup is often done is usually less than ideal (e.g., backing up on a local drive). Backup may be convenient, but in most cases it is not really secure.
Backing up files by duplicating them on the same hard drive partition as the original files gives no protection in the event of:
Hard drive crash
Computer theft
Accidental formatting of the partition or the entire hard drive
Virus attack on the local computer
Therefore, local duplication is merely a compromise for quickly saving an intermediate state. Backing up to a different partition on the same hard drive offers slightly more security, but it is still not a proper way to securely backup files.
Somewhat better is backing up to a separate internal hard drive. However, this still does not protect files in the event of:
Computer theft
Virus attack on the local computer
The aforementioned applies to permanently installed internal hard drives, so they are still not ideal for backup. Removable hard drives that are connected to the computer only during backup are better. This type of backup also reduces the risk of theft, as long as the hard drives are stored in a different location from the PC. Also, the risk of a virus infecting a removable hard drive is lower than for an internal hard drive. This risk can be further reduced if appropriate access rights are set at the operating system level. Additional hard drives can be mounted either with a swappable drawer system inside the PC or with connections as external drives. External disks can be connected with USB 2.0/Fire-Wire without measurable performance degradations. Unlike a drawer-mounted hard drive, an external drive can also be connected easily to other computers. Even using two or three external hard drives dedicated for backup is less expensive than an equivalent solution using backup tapes. A hard drive’s mechanism is sensitive to shock; but with adequate care, this is not really a problem.
If you want to transfer large amounts of data quickly and safely, you are even better off using the newer eSATA technology rather than USB or FireWire. An external eSATA hard disk is nearly as fast as an internal hard disk and is an ideal storage platform for home users.