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You already know you should backup your hard drive, I don’t have to tell you that. However, you might not know that hard drive backup is there to protect you from three different threats. And when you devise your own data backup solution, you’d better be sure that it addresses all of them.

1. Hard drive failure: Commonly known as a disk crash, but technically not all hard drive failures are crashes. Anyway, to make a long story short, this type of threat includes all instances where the disk hardware just fails out of its own volition.

2. External damage: This is anything that can do damage that goes beyond just the disk drive and includes natural disasters, theft, lightning strikes, misbehaving software, viruses, terrorism, nuclear war, etc. Well the last two items are hopefully a little extreme.

3. Accidental deletion of files: This threat is also a kind of external damage, with the exception that you may not always notice something got erased in time to save it. Picture the following scenario: You accidentally erase a crucial file, but it goes unnoticed. You perform a full backup of your computer, and only later you notice a file is gone. You want to restore it from backup, but guess what, you just backed up your computer the way it was after the file was gone, so it’s also gone from the backup.

Now let’s look at some possible backup solutions and see how they protect you against each of the threats.

RAID

The acronym RAID stands for Redundant Array of Independent Disks, and to put it simply, it’s an arrangement where the same data is written into more than one disk simultaneously, thereby automatically creating redundant copies of all the data. A RAID offers a very convenient solution to protect against hard drive failure, but does not protect against external damage or accidental deletion. However, hard drive failure is the leading cause of data loss, and it’s something you have absolutely no control over.

For a personal computer, a RAID is most commonly implemented using two ordinary hard disk drives linked together to operate in parallel. Most mother-board hardware supports RAID, and need only be configured properly. A RAID will make a computer system a bit more expensive because it doubles the cost of disk storage simply by virtue of an additional hard drive. But with the rapidly falling prices of hard drives, the second redundant disk is well worth it as part of a comprehensive backup strategy.

RAID’s are not currently available for laptop computers however. The miniaturization and space constraints of a laptop make a second redundant disk more of a nuisance than laptop manufacturers would like to contend with.

External Hard Drive

An external hard drive will protect you against hard drive failure, and potentially against external damage and accidental deletion, but it really depends on how you use it.

In order to gain total protection against external damage, an external hard-drive must be stored off-site. If your house burns down (god forbid) what good is a external hard drive that’s stored next to your computer. If you have close friends or family you can trust 100%, you can store your external hard drive there, if not, you can put it in a safety deposit box at a bank.

There’s one problem with off-site storage, however, and that’s the hassle of going back and forth to backup and place your drive off-site again. A good solution is to have two external backup drives. One drive you keep next to your computer, and use if for frequent backups, and the other one you keep off-site and use for less frequent backups. You can do weekly or monthly off-site backups, or whatever time interval you’re comfortable with. If disaster strikes, you will potentially lose an interval of data, but hey, those disasters are very rare.

Another thing you can do to protect yourself from losing your most frequently changed data (such as your work documents) should disaster strike, is back up those few files on to a USB memory stick and carry it with you at all times. This way, your entire computer is protected with an off-site external drive, and your most frequently changed files are protected as well on your USB device.

You can protect yourself against accidental deletion by keeping old versions of your backups. The more of a history you keep, the more protected you are. The idea is to give it enough time so that an accidentally deleted files does not go unnoticed for longer than your backup history. You may want to keep some files forever. For example, digital photograph are files don’t change over time, just more of them come in. A possible strategy is to keep every year of photographs in a separate folder that is then permanently stored without change. A good way to preserve such immutable data is to archive it onto DVD ROM’s, which are much more difficult to delete than the read-write magnetic media found in external hard drives.

A good backup software will help you manage the process of backup and storage of old versions of files. It’s beyond the scope of this article to review backup software, but I’ll just mention that if you’re a Mac user (like I am) and run the Leopard OS, then you’re all set with the great Time Machine backup utility, which manages versioned backups and restores. And if you still haven’t gotten an external drive for your Mac, you should consider the Time Capsule. Otherwise, a cheaper USB connected hard drive enclosure will do.

Online Backup

With online backup, your files are backed up onto a remote backup service across the Internet. In a sense, this data backup solution is similar to an external hard drive backup, however it has the great advantage of being way off site, and therefore saves you the hassle of manual transporting your backup somewhere else to protect against disasters. Online backup is also especially convenient for use with laptops on the go.

The the disadvantage of online backup is that transfer speeds are slow relatively to a disk that’s physically attached to your computer. Your initial backup will likely take a long time to complete, but subsequently only those files that have changed since the last backup need be saved, and thus your backup is kept up to date in a timely manner.

Devising Good Hard Drive Backup Strategies

Are you comfortable with not having any backup at all? After reading all this, you better not be. So what happens if your hard drive crashes, or other disaster strikes? You have a backup and that’s great. However, when that happens, you’re left with only one copy of your files, and that means you still have your files, but they’re not backed up anywhere anymore. And furthermore, it’s not out of the realm of possibility to discover your one backup is not working or available just when you need it. It’s like discovering your spare tire is also flat.

And that’s why you should always have two forms of backup ready, at least for your most important files. Your second backup doesn’t have to be as up to date as your primary, it all depends on your comfort level with losing recent data. But it’s always a good idea to have a backup to the backup. Online backup centers will usually boast their own multiple backup scheme, but don’t let that fool you into thinking that you don’t need to provide for your own secondary backup. You can never really know what’s going on at a remove backup center. An employee can make a mistake, or want to take vengeance upon the company. And if you lose your online backup, all they’ll say is that they’re sorry and possibly give you a refund for the few dollars you’ve spent with them.

Here are two solid backup strategies:

1. Two external drives, one off-site for occasional backups and the other on-site for frequent backups.
2. Online backup for frequent off-site backups, and an external drive for occasional backups.

For a desktop computer, I advise you also add another layer of protection with a RAID. For laptop computers, which can not hold an internal RAID, external RAID drives is an option. Apple’s Time Capsule external drive, which can also be used with a PC, is a RAID.

Final Words About Encrypting Backup Disk

Be very careful with encrypted backup disks. Data security and data integrity are often conflicting goals. If you encrypt a disk, you run the risk of not being able to decrypt it. I would suggest only encrypting whole disks that are at high risk of being stolen, such as disks you travel with. Otherwise, just encrypt the individual files your deem to be a high security risk. But of course, since I don’t know your individual situation, you must use your own judgment.