Imaging software is a type of backup software that takes a snapshot of a drive with the ability to restore the image to the same drive or a new drive, should it be required. The drive’s image can be compressed to save space, though compression makes the imaging process take longer. While an image can be stored on the same drive that the image is made from, it’s safer to store it on a separate drive in case of catastrophic failure of the source drive.
Imaging software packages vary in their implementations, but basically the software scans the targeted drive making a sector-by-sector map that it stores in a compressed state. Compressed files cannot be accessed directly, just like a zipped file must be extracted before it can be used. Therefore, if it becomes necessary to restore the image, the same software must be used to decompress the image and copy it to the targeted drive. This can be a new drive, or a drive that became corrupted.
If the restore process is required for the boot drive, (the drive that contains the operating system), it requires a bootable, self-contained CD made from, or provided by, the imaging software program. Booting from this CD will allow the user to direct the software to the archived disk image, then start the process of restoring the image to the boot drive. Once the image is restored, the system can be rebooted from the hard disk.
If a new, unpartitioned drive is the target, you might need to create a partition first, before the disk image can be restored. The new partition must be at least as large as the original drive or larger.
In general, disk imaging is traditionally considered an all-or-nothing method of whole-disk backup and restore, lacking the ability to run incremental backups or selectively target folders or files. However, some imaging software will allow one or both of these options. For example, Runtime Software™’s DriveImage XML Backup©, free for personal use, can mount the compressed image and, using a built-in file manager, allow the user to browse the image and select specific files or folders to restore. Other disk imaging software will allow incremental backups, saving time by not having to image the entire drive with each backup.
Most imaging program packages also offer other methods of backup, such as disk cloning. Disk cloning requires a dedicated, separate hard disk, making it a more expensive method than disk imaging but also more convenient and trouble-free. Disk cloning creates a twin or clone of the source drive, right down to the partitions and formatting or file system. Disk cloning requires the imaging software reboot the computer a few times during the cloning process so that files that are in use can be copied to the clone.
The advantage of a cloned disk is that if the main drive fails, the clone does not need to be restored with proprietary imaging software before it can be used. Instead, the computer can just be booted from the clone with no downtime and zero worries. A cloned drive can also be accessed and manipulated through a file manager at any time, just like a regular drive. This can be handy for manually swapping files or deleting items no longer required between scheduled backups.
If you like the idea of cloning, you needn’t have the same size drive as the one you wish to clone. Disk imaging software like Acronis® True Image® can automatically adjust partition size on the targeted drive accordingly, assuming enough space for the data. If a larger drive is used you can choose to increase partition or drive size respectively, or maintain the configuration of the source drive on the clone. The latter choice simply leaves unformatted, unused space on the larger drive that you can later recover and use if desired.