Backups are defined as making copies of your data onto media not normally connected to your computer in case something goes wrong with your computer. The definition is simple enough, but time and money make the actual process of doing regular backups much more complicated. (Note: this article is intended for home/hobbyist users)

Why make backups?

Backups should be made regularly because computers are not 100% reliable. Hard disks malfunction, viruses and worms corrupt data, and people sometimes accidentally delete a document that they spent hours working on. Having a backup means you can recover from such things, with little data lost.

If you are a business, your data is the heart of your business. Things like customer data, supply data, and business plans are all kept on computer. Not having a backup strategy in place means that a single malfunction can leave your business without any data, thus placing the future of the business in jeopardy.

Basic Issues

To start with, there are some basic issues regarding choices of backup technology:

1. Time - How long will backups take? Quicker is usually better. However, longer backups are okay if the computer will not be used for extended periods of time, such as overnight.
    

2. Money - Some backup solutions cost more than others. Sure, you could back up your collection of MP3s to a DLT drive every night, but the drive alone would cost thousands of dollars, something that is out of the reach of home users.
    

3. Labor - How difficult is it to make backups? If you have backup software, making a backup can be as easy as pushing a button and walking away. If you don't have backup software, the process of making a backup can consist of copying many folders to a CD, which can be cumbersome and error prone. I'll talk about this more later.
    

Considerations for choosing a backup strategy

Now, I'd like to talk about a few considerations that should be made when choosing a backup strategy:

• Backups should be made to seperate media that you can pickup and take with you. This way, copies of your data can be kept off-site, such as in another building. This helps protect against fires/floods/other disasters which may obliterate the building where your computer is. This also means that copying data to another hard drive inside your computer is not an effective backup.
   

• The frequency of your backups should be dictated by how much data you would like to lose if there is a problem on your machine. For example, if you enter a significant amount of data every day, you should be backing up every day. If you rarely enter new data, then backups once per week might be okay.
   

• Backups should be tested. Make sure that you can read the backup you just wrote. Nothing is worse than having a disaster and discovering that your backups are unreadable for some reason or another. If you are burning CDs or DVDs, it is usually sufficient to have the burner program "verify" the disk after it is written.
   

• Backups should be made regularly. Get into the habit of doing it every night or every week.
   

What to back up?

This brings us to the question of "what should be backed up?" I usually approach this problem by seperating files into two categories: "mutable" and "immutable" (or "static").

• Mutable files are those which change frequently. Examples of mutable files would be things such as regularly updated Word Documents, email archives, or pogram source code. These things should be backed up frequently.
   

• "Immutable" files would be those files which do not change on a regular basis. Examples would include collections of JPGs, MP3s, and other media files. Also included in this category would be .ZIP files for programs which you have downloaded. (You do save those, don't you?) Since immutable things do not change on a regular basis, they do not need to be backed up regularly. Making two or three backups of a particular directory of MP3s should be sufficient.
   

Different kinds of media for backups

On the subject of media to back up to, I'll give an overview of what is generally available for backups:

• Copying data to a remote server - If you are fortunate enough to have a lot of space on a remote machine (such as a webserver), you can always copy data over the network. The main advantage this offers is the ability to backup and move the data offsite at the same time. There are several disadvantages, however: first, if the network is slow or down, you may have problems trying to restore a backup. Second, if you have several Gigabytes of data to back up, you may run into space issues on the remote host. Third, if you are backing up to a machine you do not own, you will have very little control over what happens to the machine. If the hosting provider decides that you didn't pay the bill and locks you out, you'll be without access to your backups. Unless you own the remote the system, I do not recommend backing up to a remote machine.
   

• Copying data to a local server - Let's say you own two computers. You could perform a backup of your data by copying it to the other machine. This method is useful for doing very quick backups of your data, since it would be done over a fast LAN connection. One of the disadvantages of this method is that it would be difficult to take the backup with you, since it resides on the other machine's hard disk. This method does have value for making a quick backup of the day's data and should not be discounted as a first line of backup.
   

• Another hard drive in the same computer - This method is probably the fastest of all. I do not recommend it, however, because if a virus or software bug causes your data to be erased, there is no guarantee the same thing won't happen to the second hard disk as well. As with copying the data to another machine, it is also difficult to take the backup with you.
   

• Tape drives - Tape driver are slow to access (you have to advance to the spot on the tape), expensive, and prone to jamming because of the many moving parts. But, they hold a lot of data. Well into the hundreds of Gigabytes for the more expensive drives. The only problem here is that they are priced well out of range for home users. That's about all I'll say about them here.
   

• External hard drives - Faster and cheaper than tape drives, they have a few disadvantages. First, they are expensive compared to other media. Second, they have moving parts and are rather fragile. Third, since it is easy to copy things to them, there is the tempation to copy working files to them and suddenly you are in a situation where you have unique data on what is supposed to be a backup device, thereby defeating the purpose of the backup.
   

• CD-R/DVD-R - CD-Rs and DVD-Rs are both fast and cheap. Since the cheapest ones are not rewriteable, it provides two important benefits: first, it removes the risk of putting unique data on a disk and second, once a backup is made, you know that you'll have a snapshot of files from that date pretty much forever. (well, the life of the disk, at least) Furthermore, virtually any computer on the market can read CDs and DVDs. This means if your residence or business is destroyed and all you have is a CD with your data on it, you can copy it on to nearly any computer and get working again.
   

  For home users and small business users, I feel that optical disks are the best choice for backups.
   

Recommendations

As far as recommendations for backups go, that depends on your situation. Here's a few "rules of thumb" that work for me:

1. First, I keep ALL of my data in a directory called "Data". I have immutable data in a directory called "Static", and mutable data kept in a directory called "Dynamic".
2. Every few days, I back up all of my data (mutable and immutable) to my other machine, and/or my external hard drive.
    

3. About once a month, I burn a new CD with the mutable data, write the date on the CD, and move it offsite.
4. About once every 1-2 months, I burn a CD or DVD with any new immutable data, such as collections of pictures, movies, or MP3s, and move that offsite.
    

5. Keeping all of the data in one directory makes it much easier to see how much data you have to back up (just view properties on the folder), and to do perform the backups, since all it involves is dragging a single folder into your CD/DVD burning application.
    

Pitsfalls to avoid

The following are some traps that are to be avoided when making backups:

• RAID-1 is not a form of backup! While RAID-1 (or RAID-5) is a great way to have extra copies of data on hand in case a disk fails, it's not a form of backup because it's not a seperate set of the data. For example, if you type "rm -rf /" on a UNIX machine with RAID-1, it will happily delete all of the data on both disks.
   

• Backups that take up two or more disks. One of your goals should be to fit an entire set of data onto a single disk. If a backup takes more than one disk, it makes the process more complicated (which means greater opportunity for mistakes), and requries human intervention halfway through to change disks.
   

  If you find that you have mutable data taking up more than a single DVD, you might want to see if all of that data is still mutable. Is there something in there which you can put in the immutable directory and burn to a DVD for archival, perhaps?
   

• Custom media. This mostly applies to tapes. As mentioned above, CDs and DVDs can be readon nearly any computer. If you are doing backups to tape, then you need a special drive to read the tapes. If the drive goes bad, you will be unable to perform (or read from) backups until the drive is repaired. And since tape drives tend to be expensive, it's usually not an option for a home user to have a second tape drive as a spare. This is another reason to go with CDs or DVDs.
   

I apologize for this article being so long, but I hope it gives you an idea to some of the issues that come into play when choosing a backup strategy and making regular backups. If you have any questions about this article or backup strategies in general, feel free to send me email and I will be happy to help.

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