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Rapid, Reliable, and Automated method for Virtual Machine Cloning Disclosure Number: IPCOM000132284D
Original Publication Date: 2005-Dec-06
Included in the Prior Art Database: 2005-Dec-06
Document File: 3 page(s) / 53K

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This article describes a rapid image cloning method for use with a virtualization system. By using a differencing mode on the block-level storage hosting the virtual disk images, virtual machine clones can be created in a rapid, space efficient and reliable manner.

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Rapid, Reliable, and Automated method for Virtual Machine Cloning

Disclosed is a method for rapidly cloning virtual machine (VM) disk images. By manipulating files representing virtual disks in differencing mode, clones of a virtual machine disk image can be created in a rapid, space efficient, and reliable manner.

    Many clustering and server compute farm environments require that the same operating system image is used across all systems. Today the process of cloning and updating these images depends on remote deployment systems that rely on network technologies such as Pre-boot eXecution Environment ( PXE) and Wake on LAN (WOL). Network-based deployment methodologies are susceptible to network problems and are constrained by available network bandwidth. These types of solutions require monitoring and configuration of the deployment system, increasing the need for human intervention. Currently, these types of solutions also require that sufficient local/logical storage is available to accommodate the entire image being installed. Remote deployments also require a large amount of time to transfer the image to the endpoint, taking the endpoint offline during the time of the image transfer and install. A solution is needed that provides a reliable, automated and fast process to ensure a set of virtual machines are consistently running the newest image.

    This article describes a method that takes advantage of currently available virtualization technologies. Deployment operations can be made more reliable by eliminating the use of WOL since the hypervisor can power control the virtual machine. Also, there is no requirement for PXE because the imaging is done via storage management, thus eliminating network dependencies for image cloning.

    Additionally, the deployment operations can be made faster by using block-level differencing in the virtual disks images. This technique uses one master volume containing a shared image to be used by all virtual machines. For each guest operating system, a small delta file needs to be manipulated per virtual machine containing differences such as the per-machine personality data -- hostname, TCP/IP configuration, etc. The deployment operation can now be fully automated because the image is prepared in a way that when deployed the endpoint can self configure, so no configuration monitoring or injection is needed to customized the computer. Cloning of the virtual machine image involves copying the small delta file and updating the personalization data for the new guest operating system.

    The following algorithm can be used to implement the rapid cloning of Windows guest operating systems in a VMware environment. The high level workflow steps to clone a VM are shown in Figure 1:

1. Generate delta image (REDO) file from Golden image
2. Copy REDO file to new Virtual Disk
3. Create a new VM to apply image
4. Power On VM in persistent mode
5. Request sysprep information from Central location and sysprep


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