One Backup (only) is a Disaster Waiting to Happen
I found your articles about thorough back ups to be very good and from experience I can say it is the most vital thing we can do
Over the new year the main hard drive hanging off my Mac died, OK I thought I’ll insert the spares in and rebuild my library. All goes well after getting the first line drives from upstairs but half way through the last drive it too dies.
Now most people I know would be in tears but I pick up the remaining drives put in a secure case and go and get the next line of spares rebuild the rest of the library and move the data around on the spare spares.
I found out long ago that hard drives left alone can freeze so I move the data around every 3 months or so. Having been frightened by the what if the third drive failed I looked at what next and took a couple of weeks burning two copies of everything on to DVD and cased them up one set going to my brothers house given that the hard drives live with my father.
I was not in tears through this as I rarely have more than 2 wks worth of work only in the house and even then I carry around that work in a shoulder bag when I go out. Anyhow I don't know if any of my events over the new year is of any use as an example of be careful to other readers as a bit of it does happen.
MPG: A single backup only is a huge risk. Hardware fails. When you really need that single backup, it is longer a backup, it’s now the master copy.
For personal data, perhaps it’s a tolerable tradeoff for low-value data, but the odds of losing your Stuff forever go way up with only one backup, especially if it’s a backup attached to the computer—this cannot be considered a proper backup because it is subject to the same perils as the computer.
For a professional responsible for customer data (wedding photos, professional records, etc), a single backup is professional negligence, and loss of data might be grounds for legal damages.
The minimum number of separate external backups that I consider defensible is three (3), preferably all stored separately, with each updated in turn on some schedule, the frequency to be determined by the value of the data that might be lost. These backups are in addition to anything attached to the computer e.g., a local clone backup or Time Machine backup—being attached to the computer means those backups cannot be counted on, because they share the same perils such as fire or theft.
What is a great all-around backup drive? The OWC Mercury Elite Pro.