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August 2013The monthly newsletter by Felgall Pty Ltd

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I assume that you know by now that it is necessary that you backup the data on your computer. If you didn't know that before then you know it now. At some point something is going to cause a loss of data on your computer and you will need a backup in order to get that data back. The something can vary from your accidentally overwriting the file through hard disk failure through to your computer being stolen or your house burning down with the computer in it. Having backup copies of your data means that you can recover your data if any incident occurs that results in the loss of your original file.

There are a number of different types of backup that you can make of your system and each can serve a different purpose. Here we are going to consider those different types and when each might be appropriate.

The two main categories of backup are those that make complete images of your hard drive and those that backup the individual files. Taking a complete image backup is the one that takes the longest to run as it has the most to backup. It is also the one that is least useful for home use as it is the one that you would use if you want to copy the current computer configuration onto a number of other identical computers without having to install everything onto each individual computer. It is also the one that you would use of you suspect that your current hard drive is about to fail and you want to transfer everything onto a new drive that you can simply swap for the doubtful one without needing to be concerned about anything else being affected by the hard drive exchange. So for the most part the backups you need to run are those that backup the individual files rather than taking an image of the entire disk.

When it comes to individual file backups your backup software should give you two or three options as to the actual type of backup that you want to perform. One of these options will be to take a full backup of every file that you want to have backed up (whether this is the entire disk drive or specific folders will depend on just what you have decided on for your backup policy since apart from your emails and documents you can probably recover most everything else by simply reinstalling). You should always take a full backup as your first backup and repeat this at regular intervals. Just how long you leave it between full backups will depend on how much you are backing up and how often it changes but not every backup needs to be a full backup as the other two types of backup are faster and still provide you with backup copies of all your changes.

An incremental backup is one that only backs up those files that have changed since the last backup was run. This provides the fastest backup since the number of files to be backed up will be smaller than for any other type of backup. The disadvantage of this type of backup is that you will need the last full backup and all of the incremental backups since then if you want to be able to restore everything back to its current state since the full backup will only allow you to restore to the point where it was made and each incremental backup (in the order they were created) will only bring things back up to the point where that specific incremental backup was taken. Also if you restore the incremental backups in the wrong order then you may replace a more recent version of a file with an older one.

A differential backup resolves the problems of an incremental backup while still avoiding the need to back up everything every time. What this type of backup does is to backup everything that has changed since the last full backup. Each time you run it the backup will backup all of the files since the last full backup. It will get quicker again after you run another full backup. To restore everything you will need the last full backup and the last differential backup.

Which of those backup types you choose to run will affect how long each backup takes and how long it will take to restore if that should be needed. The most important thing is that having chosen a backup plan that you stick to it and that you keep multiple backup copies in different locations so as to make it easy to restore individual files if needed while ensuring that you still have a backup if the worst happens.

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