What IS a backup? What does it mean to backup?

These may seem like the simplest questions, but really they are quite complex, and even heavily debated by some.  Let’s explore…

What is a backup?

The dictionary says this: “a copy or duplicate version, esp. of a file, program, or entire computer system, retained for use in the event that the originalis in some way rendered unusable.”

The key words there are “copy or duplicate”.  A backup is a second copy of something.  If you have a backup of something, that means that you have the original usable thing, and a second identical copy of that same thing that you can pull out in case the first one is lost, destroyed, stolen, burned up, or whatever.

There are many people who believe that a backup is anything that is not stored directly on your computer.  For example, they think that if you save your digital photos onto an external hard drive, you can then delete the original digital photos from your hard drive, because they are now “backed up”.  The actual word for this concept is Archive.

If you make a copy of a thing on an external hard drive, and then delete the original thing, then you still only have one copy of the thing.  If anything were to happen to that one copy, you will loose the thing.  External hard drives tend to be fairly reliable, but they still have the same weaknesses as any other hard drive, and are even more likely to be accidently dropped or smashed than a typical computer cabinet.

Many experts agree that any given thing is not sufficiently backed up until there are Three copies of the thing – one that you use, the nearby backup that’s immediately handy, and another third copy that’s stored far away from the original in case the original AND it’s backup are destroyed in some kind of fire or other natural disaster that can take out a whole building.  It depends entirely on how important the thing is.

What does it mean to back up?

To “back up” means to create a backup copy of something, and store it safely, separate from the original.

If you have a file on a disk, it is not enough to simply make another copy of the file on the same disk.  What if the disk fails?  Typically, it is good enough to copy a file to a different disk, even if that disk is in the same computer.  Then again, what if the whole computer were to be destroyed?  External hard drives make a good place to store backup copies of files.  They are physically separate from the computer itself, and can be detached and stored seperately, such as in a closet or desk-drawer.

What about Multiple Backups?

Making a backup can be as simple as just copying a file from one hard drive to another.  This is usually fine for things like digital photos, since those pretty much never change once they are taken…

However, if the file is something that gets changed frequently, it may be valuable to create many backups of the file, captured at different points in time.  If you are working on typing a document, you may want to make a backup of it on Monday, then work on it more, then make Another backup of it on Tuesday, etc.  This way, if you discover that you made a major mistake while working on the file on Tuesday, you can go back and retrieve the backup you created on Monday and continue from there.

What is a backup set?

A backup set is a collection of multiple backups of multiple documents over time.  When talking about a collection of multiple documents where some of the documents will be changed or updated over time, but other documents will remain unchanged, it may be more efficient to create a backup set.  This involves making a single “Master Backup” of all of the files in the collection, and then later making additional backups of only the files that have been changed up to that point in time.  This partial backup may be called “Differential” or “Incremental”, and when combined with the Master Backup, can be used to recover all of the files in the collection to the point as they all were after some of them were changed.

Using backup sets to maintain a backup time-line of a group of documents if much more efficient than making multiple copies of the entire set of documents.

Most computer Backup software packages offer the ability to create and maintain backup sets.  It’s usually fairly easy to work with backup sets using one of these programs, but it will still be more complex than simply making a copy of everything you want to protect on an external hard drive, and then sticking that hard drive in a safe place.

What about RAID?  Can I just use a RAID to back up?

What is RAID?

R.A.I.D., which stands for “Redundant Array of Inexpensive Drives”, is a technology that spreads data across multiple physical hard drives in a way that preserves the data even if any one of the hard drives in the group fails.

RAID IS NOT BACKUP

RAID technology does NOT protect against:

• Accidently deleting data such as when you accidently delete a file from within a program so that it can’t be pulled out of a recycle bin, or if you accidently save a new document over an old one that you didn’t want to loose
• Deliberate or Malicious vandalism of the data such as an angry child or (soon-to-be-ex) spouse who deletes important documents
• File corruption such as when a program crashes in the middle of updating a document
• File corruption or deletion such as when a virus gets on your system and starts to delete your data

RAID technology protects data against hard drive failure.  RAID is all about Availability, not Data Protection.  If you are running a business, and you can’t afford to have your computers stop working because your employees and customers would have to wait for a hard drive to be replaced, and then wait for data to be restored from a backup tape, then you would be able to benefit from using RAID to keep your system going even if a hard drive fails because the data would still be usable by those who need to use it, even while you or your IT staff works to replace the broken hard drive.

While RAID itself is NOT a backup strategy, it is perfectly acceptable to STORE your backup data ON a RAID system – As long as there’s still another copy somewhere else.  Think of RAID as “Live Storage”.  It’s really no different than having an external hard drive that is REALLY REALLY REALLY reliable.  The Drobo, for example, is a good looking device for saving your backup copies of a document to.  You can trust that the backups will be safe if a hard drive fails.  Just remember that it does not protect against accidental data deletion, corruption, or vandalism, so you still need another copy of your data to protect against those things.

Up next: What do I need to backup?