How much space do I need for a backup?

A reader lost a whole lot of family photos due to a power surge that fried his PC. Now he wants to do things the right way and make sure everything is backed up. But he has some questions:

“I’m wanting to do a backup to a thumb drive (TD) and have a few questions.

First, if I look at the computer it shows how much disc space I have used. So I need at least that much space in the TD?

Next, say I have some old data stored on the TD from a previous back up. If I use it again to do a fresh back up, does the backup record over the old data or does it go to the end of the old data and add it to the TD?”


The size needed for the backup depends on what types of files you want to back up. If you’re only looking to backup your important files like photos, videos, music, and documents, and settings, you only need the amount of space they take up on the hard drive. This can be as simple as dragging and dropping your photos folder to a thumb drive once a week. It’s a good idea to update your document and photo library backup every time you add a new document or picture.


If you want to back up the entire system including the OS and programs (This is called a system image), you’ll need the same amount of space they take up on your PC. If you back up your whole computer, including your installed programs, what you need some type of System Image software, sometimes called Disk Image. These programs make an exact copy of your hard drive, bit by bit, at the time you take the image. You would need to save this to an external drive to preserve that data. The drive should be at least as large as the amount of data you have saved on your drive. Windows 10 and 11 both offer built-in system image options.

If you choose to do incremental backups, you’ll just add the new data to your backup each time.

A system image is the quickest way to restore your computer in the case of a major failure or hard drive crash. Simply restore the image to a new hard drive and your computer is back to the exact settings it was at the time you made the image, including all your programs and saved settings.

One other thing to keep in mind. If your computer or hard drive fails completely and you cannot access the Control Panel, you will also need an installation or system repair disk in order to restore using a system image. You must be able to boot into Windows in order to restore from a system image.

To be honest, the best way to completely back up a system is to use a combination of both of these approaches. Create a system image, saved to an external drive. Make sure your drive is large enough to store the image. It’s really not a bad idea to do this once a week or so, but at the very least, once a month., if you want an up-to-date image. But continue to do a typical backup daily (or as needed) for your files and photos. That way, if something happens, you have everything pretty up to date, and whatever may not be in your system image when you restore, you can easily recover from your daily backup.

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