What are the differences between RAW and QCOW2 disk images in KVM environments, and which one should you choose?

A RAW image is a pure binary disk file that closely mirrors a physical drive. Because it lacks additional metadata layers, its performance is nearly equivalent to physical storage. RAW images can be directly attached to virtual machines and are simple to convert into other formats, making them useful as intermediary formats during migrations . They are easy to extend and interact well with systems. However, RAW does not natively support snapshots or encryption. While version control tools can simulate snapshot-like behavior, this requires additional management effort.

QCOW2, short for QEMU Copy-On-Write version 2, introduces advanced features on top of basic disk functionality . It supports copy-on-write technology, enabling efficient storage usage since the file grows only as data is written. QCOW2 supports internal snapshots, zlib compression, and AES encryption with 128-bit keys. These features make it particularly attractive in cloud or dynamic environments where flexibility and storage optimization are priorities.

Both formats can be converted using the qemu-img command-line tool. For example, converting QCOW2 to RAW requires specifying source and target formats, and vice versa .

In summary, RAW is ideal for maximum performance and simplicity, while QCOW2 is better suited for environments requiring snapshots, compression, and encryption. The right choice depends on workload priorities, performance requirements, and management capabilities.