In parallel to the file-based backup we produce with Backup Exec, there are software products that create images (snapshots) of whole volumes to back up he data contained. These images are usually stored locally on a disk oft he imaged server but can also be transported over the network or coped to removable devices.
Usually, these programs do not support backup to tape.
One big advantage of this backup method is that it is noticeable faster than file-based backups. Furthermore, image backups are usually hardware independent. This means, that an image that was created from server A can easily be restored on server B, even though server B might have completely dissimilar hardware components than server A.
In case of Backup Exec this functionality is provided by using a boot disk for the restore that allows you to add driver software after the restore is done. In detail: After the restore copied all the files back, a wizard is started that scans the server where the restore took place and verifies that all necessary drivers are available within the restored data on the hard drive. If drivers are missing, the wizard raises an alert to the user doing the restore and offers a possibility to inject the drivers from a removable drive or a network location.
Even though this sounds great, unfortunately this technology isn’t a jack of all trades solution, too. One of the disadvantages is that these software products can store the backups on disks and network shares but not on tape. Furthermore, the smallest selection that can be chosen for an image is a whole volume. This may be fine for the system volume of a server, but for a multi terabyte file server this is obviously not the right data protection solution.
Because of the ongoing success of virtualization technologies, image based backups get less important, because a backup from a virtual machine is an image anyway and the restore performance is quite similar to a “real” image. And hardware independency is no longer important, if the source and the target machine run on virtual hardware anyway.
At this point I want to point out something:
Please do not attempt to restore Active Directory Domain Controllers from a volume based image or snapshot. Because of the structure of the Active Directory, doing so might lead to irreparable damage of the database.
I’m fully aware that there are ways to use volume based images to restore a domain controller; but I’m also aware that these workarounds are quite risky and are neither recommended, nor supported by Microsoft.
Please find more information regarding the restore of Active Directory Domain Controllers in this TechNet article: http://technet.microsoft.com/en-us/library/cc535164.aspx