It's the first question you are asked any time your PC or server has crashed: Do you have a backup? It seems like such a simple question, but I've found that a lot of people, end-users and IT professionals alike, don't know how to perform a reliable backup. In fact, it's not so much the technical aspects of performing a backup that people don't understand, it's the strategy behind the backup where a lot of people fall short.

When developing a backup strategy, there are some simple questions to ask. What needs to be backed up? When and how often? Where should the backup tapes (or other media) be stored? How do you test the backup process? The old joke in our industry is that backups always work, it's the restores that are the problem.

In this column we'll discuss such strategies, and in future columns we'll look at the capabilities of specific products.

First, what needs to be backed up? For home or small businesses without a networked file server, start by making sure you save all your files in a single folder or directory. For Windows users the My Documents folder is expressly intended for this purpose. Keeping all your data in a single folder makes it much easier to back up. For larger businesses, follow this same principle, but you might need more than one directory. Make sure your users know where to store their documents!

Now that all of your data is in one location, you need to determine if you need to back up more than just your data. For home or small-business users, it might be enough to just back up the data. This means that if your PC crashes for some reason, you will need to reinstall the operating system and all the programs that you use. If you use only a small number of programs, this might be a viable option.

Most PCs nowadays ship with a "restore" CD that will put your PC back exactly the way it was when you bought it. Run the CD, restore your data, and you should be good to go. You will need to reinstall any applications or updates that you made after you bought the PC, and this is really the kicker. If you are the type to install a lot of applications, then you will benefit from backing up your entire PC, as opposed to just the data.

For large businesses this strategy of restoring the PC back to its "original" state is often used. As long as your end-users are educated to store their data on the server, restoring a PC to its original state can save your technicians a lot of time that would otherwise be spent troubleshooting problems that they've never seen before.

Why not back up the whole PC? First of all, for most people, data is less than a gigabyte, while the entire PC (including operating system and programs) is at least several gigs' worth. Your data can easily be copied to a one or two CDs or a single DVD, and most PCs nowadays come with either a CD or DVD burner. Backing up the whole PC could require multiple DVDs or even a tape drive, and is a time-consuming process.

If you decide to back up the entire PC, you might consider doing so on a monthly, quarterly or annual basis. Just don't forget to do it when the time comes!

Of course, for servers, you don't have a choice. For all but the smallest servers, you have to ensure that the entire server, operating system, applications and data are backed up. You will probably need a tape drive to back up servers and large PCs, since the tapes can hold 200 GB of data or more, while CDs are limited to about 700 megabytes and DVDs about 5 GB.

How often should you run your backups? For low to medium home users backing up data only, you might consider backing up on a weekly basis. If your files are updated and changed constantly, then your backups should be run daily.

For businesses a popular method to ensure regular backups and minimize the need for media is often referred to as "Grandfather, Father, Son." This method uses three sets of reusable media (usually tapes) for daily, weekly and monthly backup sets.

The first set, "Son," consists of your daily backups. Four tapes are used as daily backups for Monday through Thursday. These tapes will be used to perform daily backups, can be reused weekly and contain only data that has changed since the last backup.

A second set of media, called "Father," is used to perform full backups on Fridays. This media will be used on the first through fifth Friday of the month and can be reused monthly during its respective week.

The final set of media, called "Grandfather," is used to perform full backups on the last business day of each month.

This rotation scheme will back up data on a daily, weekly, monthly and quarterly basis. We recommend storing at least the Grandfather set of tapes off site and not reused. Of course, you can tailor this method to better suit your business needs.

Where do you store your CDs, DVDs or tapes? For large or small businesses, you should have some sort of off-site storage, even if it's Aunty's house in Wahiawa. At a minimum this will save your data in case of fire, flood or other catastrophes. Better yet, small fireproof cabinets or safes are relatively inexpensive. For the more prudent, a safe-deposit box at a bank is also an option.

Remember that this part of your strategy should be tempered by reality. A longtime colleague of mine used to work for a major oil company, and part of their backup strategy was to ship the backup tapes to an old salt mine in Utah, where they were stored in case of nuclear war. He pretty much ignored this aspect of his job, reasoning that if there were a nuclear war, he wouldn't be around to care if the systems were up and running.

How do you test your backups? For home users, simply copy your data directory (My Documents) to another location on your hard disk, and try and restore from your backup. If the backup fails, then you always have that copy. For businesses, ideally you would have another server configured identically to the server you are backing up and could use that server to test the backups. Certainly, this is not always possible, so you might consider testing your backup strategy before you actually start using your server for critical business purposes.

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