What Are Mirror Image Backups?

This is how you can copy a whole computer hard drive to a file

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A backup program or online backup service that creates a mirror image backup is one that backs up everything on the computer, without reservation - including all the installed software, personal files, registry, etc. - and consolidates it to just a few files.

Because of the size of mirror image backups, they are generally stored on external hard drives, network drives, or other internal drives, but sometimes DVD or BD discs are used.

The file type used for storing a mirror image backup is usually proprietary to the backup program that's being used, so they're different for each application. Sometimes no extension at all is used but that doesn't mean that it's not still custom to the program that was used to make it.

A mirror image backup is not the same as a regular file backup or clone backup.

How Are Mirror Image Backups Different Than Regular Backups?

A regular backup is probably exactly what you think of when you think of backed up files - a few files, or a collection of folders with files in them, all backed up and ready to be restored, on demand, if and when you need them.

Note: Some programs, like COMODO Backup, can perform a regular backup like this but it also supports saving the backed up files to a file (ISO, CBU, and others). However, this back-up-to-a-file way of saving the data isn't considered a mirror image because the term is used only when creating a whole hard drive image, not just an image of select folders and files.

A clone backup (sometimes confusingly called a "mirror backup") is another type of backup some programs support. This type of backup takes everything from one drive and puts it on another drive. It's a clean copy from one hard drive to another, and is helpful if you have an extra drive lying around that you'd like to store your primary files on.

After creating a clone backup, you can just swap the cloned drive with your current one to have everything in place like you did at the time of the backup.

Like a clone, a mirror image backup also saves absolutely everything that's on your computer at the time of the backup. This includes the operating system as a whole, including all of those important but hidden system files, plus all of your personal files, images, videos, documents, installed programs, temporary files... even the files you might have sitting in the Recycle Bin.

Literally everything from the hard drive that you're backing up will be stored in the mirror image backup. Because the backup is stored in just a few files, you can keep them on an external hard drive that you're actively using, without compromising the backup files.

A mirror image backup is really the same thing as a clone backup but instead of copying the files to a different hard drive in a readily usable form, the files are backed up, and very often compressed as well, to a file, or a few files, that must then be restored using the original backup software.

Note: It's important to state again that a mirror image backup is just like a mirror backup (clone) but instead of copying the data to a new hard drive, it's copied into one or more files that can later be restored/copied onto a hard drive.

Some backup programs even support what's called mounting the mirror image so that you can browse through the files stored within it just as if they were backed up regularly. Some even let you copy specific files out of the mirror image backup, but not all backup programs support this and most only let you "open" the imaged data when it's time to restore it (but doing that doesn't let you view the files until everything has been restored and you can boot back into the OS).

When Is a Mirror Image Backup Useful?

Creating a mirror image backup is clearly not beneficial for all circumstances. If you want quick access to your backups or need to copy all your files onto another hard drive, then you don't want to make a mirror image file of the data.

A mirror image backup is a nice thing to have if you want to make sure that your entire hard drive can be restored as-is at some point in the future. Like mentioned above, this does mean the entire hard drive and all of its files, including junk files, deleted files, anything that might be giving you errors when you open it... but also your regular, working files like your documents, images, installed programs, etc.

Maybe you've collected lots of programs and files over the years and it's too much trouble to reinstall or re-download everything again. This is a good time to make a mirror image of the whole hard drive. If something happens to your existing drive, just restore the imaged data onto a new one.

Another time a mirror image backup is useful is right after installing the operating system. Once it's installed to the hard drive, and maybe even after you've fully updated it and added your favorite programs, you can make a mirror image of that state of the hard drive so that if you ever need to reinstall Windows (or any OS) you can just restore the mirror image backup and then start from there, skipping over all the installation steps.

Software That Support Mirror Image Backups

Mirror image backups are not a common feature in a backup program because most applications back up the files in a way that makes them easily usable after the backup, which is usually not the case for a mirror image.

AOMEI Backupper is one example of a free program that can create mirror image backups. When you choose that option in the program, it will create an ADI file that holds all of the data contained on the source hard drive.