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In this recipe, we listed the supported disk image formats by QEMU. The following is a brief description of the most common types that you might encounter:

• raw: Raw disk image format. This is the default format and can be one of the fastest file-based formats. If you format this image with a filesystem that supports holes, for example, EXT3, then only sectors that have data will use space. The main drawback of the raw images is the lack of features, making them ideal for testing and quick prototyping. 
• qcow2: As we mentioned in the previous section, this is one of the most feature-rich formats. It supports VM snapshots, compression, and encryption for the price of slightly reduced performance.
• qcow: This is an older QEMU image format that supports backing files, compact image files, encryption, and compression.
• dmg: This is the Mac disk image format. The Mac disk image provides secure password protection and compression, and it is most commonly used to distribute software, rather than running virtual machines.
• nbd: The network block device, typically used for accessing remote storage devices. 
• vdi: This disk format is used by the Oracle VirtualBox software and can be used to run virtual machines on various CPU platforms.
• vmdk: This is the VMware disk image type, where a single virtual hard disk can span multiple files.
• vhdx: Microsoft Hyper-V uses this image format. It provides large storage capacity, data corruption protection during power failures and read/write optimization for larger disk images.

In this book, we are going to use the raw and qcow2 disk formats, as they provide the best performance and toolset for running and manipulating them.