Disk cloning is the process of creating a 1-to-1 copy of a hard disk drive (HDD) or solid-state drive (SSD), not just its files. Disk cloning may be used for upgrading a disk or replacing an aging disk with a fresh one. In this case, the clone can replace the original disk in its host computer. Disk cloning may also be used for disaster recovery or forensics. In the context of backup software, disk cloning is very similar to disk imaging; in case of the latter, a 1-to-1 copy of a disk is created inside a disk image file.
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A disk cloning program needs to be able to read even protected operating system files on the source disk, and must guarantee that the system is in a consistent state at the time of reading. It must also overwrite any operating system already present on the destination disk. To simplify these tasks, most disk cloning programs can run under an operating system different from the native operating system of the host computer, for example, MS-DOS or an equivalent such as PC DOS or DR-DOS, or Linux. The computer is booted from this operating system, the cloning program is loaded and copies the computer's file system. Many programs can clone a disk, or make an image, from within the running system, with special provision for copying open files; but an image cannot be restored onto the Windows System Drive under Windows.
A disc cloning program must have device drivers or equivalent for all devices used. The manufacturers of some devices do not provide suitable drivers, so the manufacturers of disk cloning software must write their own drivers, or include device access functionality in some other way. This applies to tape drives, CD and DVD readers and writers, and USB and FireWire drives. Cloning software contains its own TCP/IP stack for multicast transfer of data where required.
The simplest method of cloning a disk is to have both the source and destination disks present in the same machine, but this is often not possible. Disk cloning programs can link two computers by a parallel cable, or save and load images to an external USB drive or network drive. As disk images tend to be very large (usually a minimum of several hundred MB), performing several clones at a time puts excessive stress on a network. The solution is to use multicast technology. This allows a single image to be sent simultaneously to many machines without putting greater stress on the network than sending an image to a single machine.
Although disk cloning programs are not primarily backup programs, they are sometimes used as such. A key feature of a backup program is to allow the retrieval of individual files without needing to restore the entire backup. Disk cloning programs either provide a Windows Explorer-like program to browse image files and extract individual files from them, or allow an image file to be mounted as a read-only filesystem within Windows Explorer.
Some such programs allow deletion of files from images, and addition of new files.
- Comparison of disk cloning software
- Disk mirroring
- Disk image
- Live USB
- Recovery disc
- Security Identifier
- Gordon, Whitson (4 September 2018). "How to Clone a Hard Drive". PC Magazine. Ziff Davis.
- Martin, Jim (2 July 2019). "Upgrading to a new laptop or hard drive? These apps will clone the data from the old drive in next to no time". Tech Advisor. IDG.
- Hayes, Darren R. (2014). A Practical Guide to Computer Forensics Investigations. Pearson Education. pp. 86–87. ISBN 9780132756150.
- Nikkel, Bruce (2016). Practical Forensic Imaging: Securing Digital Evidence with Linux Tools. No Starch Press. p. 219. ISBN 9781593278007.