Flash memory and tape
USB sticks (sometimes called thumb drives) loaded with non-volatile flash memory can be another good backup choice, with prices dropping considerably over the past year. A couple of my clients prefer using flash memory drives for document backups because they're so small and convenient to transport.
Tape cartridges are yet another option. I'm no longer as big a fan as I once was of tape, despite the low cost per gigabyte, large storage capacity, and durability of the medium. I have two principal concerns.
First, there are more than a dozen different tape formats. Tape cartridges that appear physically similar can store data in incompatible formats. This can make recovering data quickly at an alternate work site difficult.
Second, tape is a sequential-access medium, as opposed to the random-access nature of most storage alternatives. Random-access means the PC can move directly to where the data is stored on the media, with near instantaneous access, as with a hard drive. Sequential access means the PC must always start at the beginning of the media, then advance in sequence until the data is located on the tape.
With sequential media, recovering deleted email messages sent or received over a period of several months from daily backups could take hours: You must wait while each tape slowly winds its way to the required data. Think you'd never need to do this? Wait until your business gets hit with litigation that demands discovery of electronic documents.
External hard drives
Hard drives can be excellent storage media for backups, since they're fast and high in storage capacity. Some vendors offer external hard drives that you can plug into your PC or server; these products are perfect for backups. Some external drives come bundled with backup software; you simply push a button on the drive to start the backup.
External drives with a USB 2.0, Firewire, or eSATA connection will be fast enough to keep backup times manageable.
There's also a class of products called network-attached storage devices for greater backup needs.
For businesses with up to 8GB or so of important data, either a USB stick or DVD burner would work well; DVDs make it easy and inexpensive to maintain backups made over time.
I suggest that businesses with greater storage requirements use external hard drives.
Periodic rotation and transport of back-up media to off-site storage will protect against theft or loss due to destruction of the premises.
I recommend maintaining a minimum of three backup generations. Backup A can be attached to the computer or network. Backup B can be stored securely on premises. Backup C should be stored safely off-site. Then rotate the backups, taking backup B off-site, attaching backup C to the computer, and moving A elsewhere in the office.
A small owner-managed business may opt to store the off-site backup at the owner's home; an alternative is to rent a box in a bank vault. Larger businesses with multiple locations may swap backups between sites. Some small businesses may make similar swap arrangements.
If you use a courier or other common carrier to transport your backup to another location, I strongly recommend that you encrypt the data. If the backup is lost or falls into the wrong hands en route, encryption will help ensure that confidential business data remains confidential.