Hard Drive Cloning and Imaging

Hard drive cloning and imaging refer to two approaches to copying an entire hard drive. Each has its advantages and disadvantages, and both approaches have their adherents and detractors; and more than a few fights have broken out between skinny-armed geeks about which method is better. The Backup Nut, of course, is above such squabbles; I merely want my flock to do some sort of backup. So I'll present both methods, and let you use your free will to choose which works for you.

Hard Drive Imaging

Hard drive imaging consists of copying the entire contents of a hard drive (sometimes minus certain files, like the pagefile and temp files) to some other medium. Often this is a hard drive, although it can be almost any media that is of sufficient size to hold the image.

Most hard drive imaging programs, like Acronis True Image, also include bootable media that allow the system to be restored even if the computer will not boot. You can even try it risk-free: Click for an Acronis True Image Home 2010 free download. 30-days trial!

Drive imaging has many advantages, including:

The ability to make incremental and differential backups. This not only saves space, but also allows a computer to be restored to a point prior to the most recent backup, if needed. This can be useful if a problem's onset can be pinpointed to the time between two backups.
Remote storage capability. Multiple copies of drive snapshots and interim backups can be stored on a network drive away from the host computer. In the event the backup is needed and the network drive is not accessible to the host computer, the backup image can be copied using another computer on the network, or sometime even directly extracted to a hard drive using another computer.

On the down side, if downtime is critical, the time required to restore a complete hard drive from a backup image can be significantly longer than that required to get the system up and running using a cloned drive. In addition, images are intended to be restored to the machine from which they were created. Extracting individual files and folders can be cumbersome if the original machine is not repairable.

Hard Drive Cloning

Hard drive cloning differs from imaging in that an actual, bootable clone of the hard drive is created. Some programs, like Casper 5.0 Hard Disk Cloning Software, are able to do this from within Windows using the Volume Copy Shadow Service. Others must be run from bootable media.

Hard drive cloning has some significant advantages, especially when avoiding downtime is critical. For example:

Extremely short downtime. Restoring a computer using a cloned drive takes literally minutes, as the clone is a bootable copy of the original drive. Simply swap the clone for the failed drive, and you're up and running.
Simplicity. When using a program like Casper, cloning can be scheduled to happen automatically, from within Windows. There is no need to boot into removable media, change tapes or disks, or do anything, actually.
Easy access to data. In the event a document is accidentally deleted, for example, it can be accessed from the cloned drive simply by using Windows Explorer.

Most cloning software can also clone an internal drive to an external USB or Firewire drive. This is very convenient (especially for laptops) and also allows the drive to be disconnected between backups to prevent virus infection and reduce power consumption. But if you choose to go this route, make absolutely certain that the hard drive inside the internal enclosure is of the same physical size, is of at least the same capacity, and has the same interface (PATA, SATA, or SCSI) as the internal drive.

In other words, the drive inside the enclosure should be capable of being removed from the enclosure and installed inside the computer, because that's exactly what will need to be done if the clone is ever pressed into service.

There are some disadvantages to cloning, especially when using a second internal hard drive. A cloned hard drive might be taken down by a power surge or hard drive controller failure, or the backup drive might become infected by a virus. These risks can be reduced by using an external drive and disconnecting it between backups, and always performing a virus scan on the main drive before cloning it.

In addition, an internally-mounted drive (or an external drive in the same location as the host computer) could be stolen, vandalized, or destroyed along with the computer itself, leaving you with no backup. Finally, most cloning programs don't support incremental or differential backups, making it impossible to restore to a time prior to the most recent backup.

The Backup Nut's Recommendation

Having done more than my share of computer restores, I hesitate to consider either hard drive cloning or hard drive imaging to be complete backup solutions. I look at them mainly as downtime prevention strategies, and they're very good for that purpose.

For a complete backup solution, I recommend that you clone or image the hard drive and use a a network backup solution like Mozy Remote Backup for your critical documents. That, dear brothers and sisters, will put your backup strategy on a par with that of the Backup Nut himself, glory be.