Virtual machines treat the image set as a physical drive. Virtual hard disk images tend to be stored as either a collection of files (where each one is typically 2GB in size), or as a single file. ![]() either the VHD format used by Microsoft's Hyper-V, the VDI format used by Oracle Corporation's VirtualBox, the VMDK format used for VMware virtual machines, or the QCOW format used by QEMU). A hard disk drive or solid-state drive in a virtual machine is implemented as a disk image (i.e. Further, there are less issues with wear and tear. This can also be faster than reading from the physical optical medium. Virtual machines emulate a CD/DVD drive by reading an ISO image. In cloud computing, creating a virtual disk image of optical media or a hard disk drive is typically done to make the content available to one or more virtual machines. The purposes of imaging the disk is to not only discover evidence preserved in digital information but also to examine the drive to gather clues of how the crime was committed. Unlike disk imaging for other purposes, digital forensic applications take a bit-by-bit copy to ensure forensic soundness. Often, these images are also hashed to verify their integrity and that they have not been altered since being created. Uses Digital forensics įorensic imaging is the process of creating a bit-by-bit copy of the data on the drive, including files, metadata, volume information, filesystems and their structure. ![]() A virtual burner, by definition, appears as a disc drive in the system with writing capabilities (as opposed to conventional disc authoring programs that can create virtual disk images), thus allowing software that can burn discs to create virtual discs. Instead of writing data to an actual disc, it creates a virtual disk image. A virtual disk writer or virtual burner is a computer program that emulates an actual disc authoring device such as a CD writer or DVD writer. Apple Disk Copy can be used on Classic Mac OS and macOS systems to create and write disk image files.Īuthoring software for CDs/DVDs such as Nero Burning ROM can generate and load disk images for optical media. In Unix or similar systems the dd program can be used to create raw disk images. For example, RawWrite and WinImage create floppy disk image files for MS-DOS and Microsoft Windows. The software required varies according to the type of disk image that needs to be created. Typically, disk imaging requires a third party disk imaging program or backup software. Disk images became much more popular when floppy disk media became popular, where replication or storage of an exact structure was necessary and efficient, especially in the case of copy protected floppy disks.ĭisk image creation is called disk imaging and is often time consuming, even with a fast computer, because the entire disk must be copied. Early ones were as small as 5 megabytes and as large as 330 megabytes, and the copy medium was magnetic tape, which ran as large as 200 megabytes per reel. ![]() Background ĭisk images were originally (in the late 1960s) used for backup and disk cloning of mainframe disk media. Despite the benefits of disk imaging the storage costs can be high, management can be difficult and they can be time consuming to create. Proprietary formats are typically used by disk imaging software. Virtual disk images (such as VHD and VMDK) are intended to be used for cloud computing, ISO images are intended to emulate optical media and raw disk images are used for forensic purposes. Disk images can be made in a variety of formats depending on the purpose. Disk imaging is done for a variety of purposes including digital forensics, cloud computing, system administration, as part of a backup strategy, and legacy emulation as part of a digital preservation strategy. Compression and deduplication are commonly used to reduce the size of the image file set. Traditionally, disk images were bit-by-bit copies of every sector on a hard disk often created for digital forensic purposes, but it is now common to only copy allocated data to reduce storage space. For ISO 9660 image files, see ISO image.Ī disk image is a snapshot of a storage device's structure and data typically stored in one or more computer files on another storage device.
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