Backup: The best way to backup data files is to get one of those USB flash drives (memory sticks). You can get a 2 GB (Gigabyte) flash drive at Best Buy or Staples for less than $10. 2 GB is enough to hold all of your text data, financial records, notes, email, ... (My genealogy files with about 1000 entries are all less than 500 KB, that would take up 1/2,000 of the space)

For backing multi-media files (music, pictures, movies) I'd recommend an external usb hard disk. They are available at costco, best buy, .... for less than $50 you can get 500GB, enough to copy your whole hard disk.

You can just copy your files to the backup device or get a program which will look at what files have been updated since the last backup and only copy them, which will be faster if you have a lot of files.

Cloud Backup:
You can backup over the Internet to services like:
See: 40 Online Backup Services Reviewed (Updated January 2014) |

You can create your own cloud backup to a hard disk in your home.
Pogoplug is a device connecting a USB drive to your network that can be accessed remotely so you can backup your computer or mobile device from anywhere.
See: and Pogoplug Rating |

Many backup programs like Time Machine on the Macintosh save the data in a proprietary format so you cannot just plug in the backup disk and read the files without the time machine software to decode them.
You can do a strait copy but the file system format may restrict you to reading on the same type of computer Mac (HFS) or Windows (NTFS). If you format your backup drive as FAT 32 it can be read or written from either a Mac or Windows system. Backup terms are not used consistently:

A duplicate is a complete, exact copy of your entire hard disk that (if it's stored on, or restored onto, a hard disk) you can use to start up your computer if necessary. Duplicates are wonderful because they enable you to get back up and running extremely quickly--in some cases, with only minutes of down time.

But most software capable of making a bootable duplicate can also duplicate incrementally--meaning that after the first time, updating your duplicate to reflect the current state of your hard disk requires only copying the files that are new or different.

Duplicates provide no insurance against damaged or accidentally deleted files.

The Archive Sometimes referred to simply as a backup, an archive contains copies of your files as they appeared at multiple points in time.

Backup programs typically perform an incremental archive. This means that on subsequent runs, the software scans the files in the folders you've designated and copies only those files that are new (or newly modified) since the last backup. To be truly useful, archives should also be additive, meaning the backup program adds the new or changed files to the archive without overwriting the files already there.

Some people suggest performing a full archive--that is, archiving every single file on your disk, just as you do when creating a duplicate. Others suggest performing a selective archive that includes only user-created data files, especially those that change frequently.

(Note: Some backup programs use the term archive to describe files that have been copied to removable media of some kind for long-term storage and then deleted from the source volume.)

synchronization means maintaining identical copies of a file, folder, or even an entire disk in two or more locations.
  Problems: Doesn't save old versions.

RAID stands for Redundant Array of Independent (or Inexpensive) Disks; it's a way of combining multiple physical hard drives into a single logical volume using either software or a special hardware controller. One way to configure a RAID, known as mirroring, is to have the same data written simultaneously to two or more drives. If any one drive fails, another can take over instantly and seamlessly with no loss of data and no down time; you can then replace the faulty drive at your leisure.

Incremental backup, only the files changed or added since the last time the backup ran are added to the archive.

Differential backup, all the files changed or added since the initial full backup are added to the archive.

Backups are far more likely to happen regularly if your backup software runs automatically on a schedule.

You should alternate between two or more sets of backup media for greater safety.

Most experts recommend using at least three sets, of which one is always stored off-site.

External Hard Drive Review: Best Backup External Hard Drive at
USB Flash Drive Review: Best Flash Drive - ConsumerSearch

last updated 24 Apr 2005