Drives, images, and virtual disks: A guide to storage terms & concepts

The term hard drive refers to the actual storage medium — either in the classic sense with rotating magnetic discs (HDD) or as a modern SSD with flash memory. The term drive refers to the electronics and technology that handle reading and writing on these storage devices. In practice, both are usually combined in one device. Even SSDs without mechanical parts are still referred to as “drives.”

Partitions are logical subdivisions of a data carrier. They organize the memory, but are initially empty and unusable. Only when a partition is formatted and assigned a file system does it become a volume. This appears in the operating system as an independent drive with a letter such as “C:” or “D:.” A hard drive can contain multiple partitions and, therefore, multiple volumes.

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Virtual hard disks, such as those used in virtualization programs like VirtualBox or VMware, are files that behave like real data carriers. Virtual partitions are also possible, for example, when several physical areas are combined into one logical storage. This technology is often used in Linux.

An image is a complete copy of a volume — including all data, file systems, and boot information. Images are used to back up or restore a system. To access an image, it must be mounted with special software. macOS uses so-called containers with the APFS file system. These containers hold multiple volumes that dynamically share storage space, offering more flexibility than classic partitions, whose sizes are fixed. Containers allow for more efficient use of available memory.

In short: hard disks and drives refer to physical components, while partitions and volumes are logical units for organizing the storage. Images are used for backup, and containers enable flexible storage management. Making a clear distinction between the terms helps you work more precisely and protect data more effectively.