Editing Disk cloning (section)

== Technical challenges ==
There are several technical challenges that need to be considered when planning to clone a drive.

=== Drive in use ===
Often, cloning software runs within the [[operating system]] which is running off of one of the drives being cloned. As a result, any attempt to clone the contents of the drive, even to a file, would result in [[data corruption]]. Consequently, the drive cloner must ensure that the data on the source drive remains in a consistent state at the time of reading. Further, in the case, that the user desires to clone to the computer's system drive, this generally cannot be done while the operating system is running. 

A common solution to cloning a drive that is in use, which is utilized by software such as [[Clonezilla|CloneZilla]], is to boot from a Linux-based operating system so the drive can be copied and/or overwritten.<ref name=":4">{{Cite book |last1=Bălan |first1=T.C. |last2=Robu |first2=D.N. |last3=Sandu |first3=F. |title=2015 IEEE 21st International Symposium for Design and Technology in Electronic Packaging (SIITME) |chapter=Ad-hoc lab computer network configuration using remote resources |date=2015 |chapter-url=https://ieeexplore.ieee.org/document/7342360 |pages=393–396 |doi=10.1109/SIITME.2015.7342360|isbn=978-1-5090-0332-7 |s2cid=39545275}}</ref><ref>Yao, J. F. J., & Carlisle, J. (2011). [https://www.researchgate.net/profile/Ghassan-Alkadi/publication/234782265_Beyond_the_computer_science_curriculum_empowering_students_for_success/links/00b4952f3c4a0924c3000000/Beyond-the-computer-science-curriculum-empowering-students-for-success.pdf#page=75 Self-support computer science lab]. ''Journal of Computing Sciences in Colleges'', ''26''(4), 64-70.</ref> This approach is not suitable for servers that need to be running all the time and cannot be shutdown routinely to perform the backup (or cloning) operation.<ref name=":1">{{Citation |last1=Grasdal |first1=Martin |title=Chapter 8 - MCSE 70-293: Planning, Implementing, and Maintaining a High-Availability Strategy |date=2003-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9781931836937500129 |work=MCSE (Exam 70-293) Study Guide |pages=559–638 |editor-last=Grasdal |editor-first=Martin |place=Rockland |publisher=Syngress |language=en |isbn=978-1-931836-93-7 |access-date=2023-01-09 |last2=Hunter |first2=Laura E. |last3=Cross |first3=Michael |last4=Hunter |first4=Laura |last5=Shinder |first5=Debra Littlejohn |last6=Shinder |first6=Thomas W. |editor2-last=Hunter |editor2-first=Laura E. |editor3-last=Cross |editor3-first=Michael |editor4-last=Hunter |editor4-first=Laura}}</ref> Further, the Linux-based operating system must provide appropriate drivers for the system's hardware. Drivers are also required for the source and destination drives and for any attached storage involved in facilitating the cloning operation such as USB, tape device and networking drivers.

Some server-based operating system incorporate mechanisms to allow the drive to be safely backed up while the system is running to overcome these challenges. For example, [[Windows Server 2003]] (and later) includes [[Shadow Copy|volume shadow service]] (VSS).<ref name=":1"/><ref>{{Cite web |last=JasonGerend |title=Volume Shadow Copy Service |url=https://learn.microsoft.com/en-us/windows-server/storage/file-server/volume-shadow-copy-service |access-date=2023-01-09 |website=learn.microsoft.com |date=7 December 2022 |language=en-us}}</ref> VSS takes a snapshot of the drive so that any changes are not written to the snapshot.<ref>Leschke, T. R. (2010). [https://redirect.cs.umbc.edu/courses/pub/www/undergraduate/courses/FYS102D/Recycle.Bin.Forensics.for.Windows7.and.Windows.Vista.Shadow.Volumes.pdf Shadow volume trash: $ Recycle. Bin forensics for Windows 7 and Windows Vista shadow volumes].</ref> The snapshot creates a virtual drive called a shadow volume that is backed up (or cloned) by the software.

=== Slow ===
Disk cloning can be time consuming, especially, for large disks because a true clone needs to copy all the data on the disk even if most data resides in unallocated drive space.<ref name=":0"/> Software solutions can determine the space in use and only copy the used data reducing the time needed to clone the drive. Some drive cloners make use of [[Multithreading (computer architecture)|multithreading]] to further speed up the cloning operation.<ref name=":0"/>