Disk images to prevent data loss from CDs and DVDs

CDs and DVDs are simple and inexpensive carriers for storing your digital files, but they also have a relatively short lifespan. It is therefore recommended to make copies of them using disk images to prevent your digital information from being lost. In this article, you’ll learn:

• What problems can lead to information loss on CDs and DVDs?
• What is a disk image and how can you use it to make backups of CDs and DVDs?
• How do you make a disk image?

How can a disk image help you?

Writeable CDs and DVDs were used extensively for storage for many years because of their low cost, high availability and easy access. But it is now widely recognised that they have a shorter lifespan than expected. Problems resulting in a loss of data can start to occur even after just two years.

The deterioration process is accelerated further by:

• heat
• humidity
• sunlight
• playback devices in poor condition
• scratches
• fingerprints
• adhesive labels on the discs
• solvents

It's impossible to guarantee the long-term preservation of information on CD-Rs and DVD-Rs even if you avoid all these threats and harmful elements. And it is still possible that the information on a writeable CD or DVD cannot be read even without any visible signs of decay or deterioration. You can read more about how writeable CDs and DVDs deteriorate in this short text on the unreliability of writeable CDs for long-term preservation (link in Dutch).

The files need to be transferred to a different carrier in order to prevent a loss of information. The easiest way to do this is to create an ISO-9660 file disk image of the CD or DVD, make a good back-up and have checking procedures. ISO-9660 is the official standard for file systems that are supported in principle by all operating systems, applications, CD players and CD software.

How do you make an ISO-9660 image?

In macOS

You don't need to install any software to make a disk image in macOS. The 'Disk Utility' application can create ISO images of CDs and DVDs.

Step 1: Place the DVD in your internal or external CD reader.

Step 2: Open the Disk Utility application which can be found in the Applications > Utilities folder. The DVD that you have read will appear in the window's sidebar.

Step 3: Select the DVD and click on 'New disk copy'.

Step 4: Choose the location where you want to save the disk image.

Step 5: From the drop-down menu, select DVD/CD master as the disk copy structure.

Step 6: Click on 'Save'. Disk Utility will make a disk image of the CD with the extension .cdr in the chosen folder.

In Windows

There are various programs available for making disk images of CDs or DVDs in Windows. 'Imgburn' is freeware that is easy to use.

Step 1: Download 'Imgburn' from this link. Note: First read this short article to install 'Imgburn' on your computer without also installing 'OpenCandy', which is adware that collects data about your online browsing behaviour.

Step 2: Once you've installed 'Imgburn', open it and select 'Create image file from disc'.

Step 3: Place the DVD in your internal or external DVD reader and select it as 'source'. The name of the DVD will appear in the software interface.

Step 4: Choose the location where you want to save the disk image.

Step 5: Click on the icon at the bottom of the window to start creating the disk image.

Step 6: After a few minutes, a message will appear to say that the operation has finished successfully.

Result

You have made a disk image of a writeable CD or DVD and saved in on a hard drive. The data on the carrier is no longer at risk of being lost due to deterioration of the DVD-R. Be aware that this is a good but not permanent solution. Hard drives also contain magneto-optical discs that are liable to decay. Make sure therefore that you also have good back-up procedures and regular integrity checks for the files.

Authors: Nastasia Vanderperren (meemoo) and Emanuel Lorrain