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Disk image
A disk image is a snapshot of a storage device's content – typically stored in a file on another storage device.
Traditionally, a disk image was relatively large because it was a bit-by-bit copy of every storage location of a device (i.e. every sector of a hard disk drive), but it is now common to only store allocated data to reduce storage space. Compression and deduplication are commonly used to further reduce the size of image files.
Disk imaging is performed for a variety of purposes including digital forensics, cloud computing, system administration, backup, and emulation for digital preservation strategy. Despite the benefits, storage costs can be high, management can be difficult and imaging can be time consuming.
Disk images can be made in a variety of formats depending on the purpose. Virtual disk images (such as VHD and VMDK) are intended to be used for cloud computing, ISO images are intended to emulate optical media, such as a CD-ROM. Raw disk images are used for forensic purposes. Proprietary formats are typically used by disk imaging software.
Disk images were originally (in the late 1960s) used for backup and disk cloning of mainframe disk media. 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. 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.
Disk image creation is called disk imaging and is often time consuming, even with a fast computer, because the entire disk must be copied. Typically, disk imaging requires a third party disk imaging program or backup software. The software required varies according to the type of disk image that needs to be created. For example, RawWrite and WinImage create floppy disk image files for MS-DOS and Microsoft Windows. In Unix or similar systems the dd program can be used to create raw disk images. Apple Disk Copy can be used on Classic Mac OS and macOS systems to create and write disk image files.
Authoring software for CDs/DVDs such as Nero Burning ROM can generate and load disk images for optical media. 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. Instead of writing data to an actual disc, it creates a virtual disk image. 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.
Forensic 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. Often, these images are also hashed to verify their integrity and that they have not been altered since being created. Unlike disk imaging for other purposes, digital forensic applications take a bit-by-bit copy to ensure forensic soundness. 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.
Hub AI
Disk image AI simulator
(@Disk image_simulator)
Disk image
A disk image is a snapshot of a storage device's content – typically stored in a file on another storage device.
Traditionally, a disk image was relatively large because it was a bit-by-bit copy of every storage location of a device (i.e. every sector of a hard disk drive), but it is now common to only store allocated data to reduce storage space. Compression and deduplication are commonly used to further reduce the size of image files.
Disk imaging is performed for a variety of purposes including digital forensics, cloud computing, system administration, backup, and emulation for digital preservation strategy. Despite the benefits, storage costs can be high, management can be difficult and imaging can be time consuming.
Disk images can be made in a variety of formats depending on the purpose. Virtual disk images (such as VHD and VMDK) are intended to be used for cloud computing, ISO images are intended to emulate optical media, such as a CD-ROM. Raw disk images are used for forensic purposes. Proprietary formats are typically used by disk imaging software.
Disk images were originally (in the late 1960s) used for backup and disk cloning of mainframe disk media. 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. 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.
Disk image creation is called disk imaging and is often time consuming, even with a fast computer, because the entire disk must be copied. Typically, disk imaging requires a third party disk imaging program or backup software. The software required varies according to the type of disk image that needs to be created. For example, RawWrite and WinImage create floppy disk image files for MS-DOS and Microsoft Windows. In Unix or similar systems the dd program can be used to create raw disk images. Apple Disk Copy can be used on Classic Mac OS and macOS systems to create and write disk image files.
Authoring software for CDs/DVDs such as Nero Burning ROM can generate and load disk images for optical media. 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. Instead of writing data to an actual disc, it creates a virtual disk image. 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.
Forensic 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. Often, these images are also hashed to verify their integrity and that they have not been altered since being created. Unlike disk imaging for other purposes, digital forensic applications take a bit-by-bit copy to ensure forensic soundness. 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.