RAW or QCOW2? A Practical Guide to KVM Disk Formats

Iris Li

Choosing the right virtual disk format can make a big difference in performance, storage efficiency, and manageability — especially in KVM/OpenStack environments. Vinchin’s clear comparison breaks down the tradeoffs between RAW (simple, near-native performance, no native encryption or snapshots) and QCOW2 (sparse growth, copy-on-write snapshots, compression and AES encryption support), explains how to convert between them with qemu-img, and recommends use cases for each.
Read: Raw vs Qcow2 Image | Which Is Better for KVM Environment?

Malcolm

Thanks for sharing! I’ve always been a bit confused about when to pick RAW vs QCOW2. The part about snapshots and compression in QCOW2 really clarifies things. Definitely going to try Vinchin’s recommendations next time I set up a KVM VM.

Marshall Beckett

Good timing — I literally had to convert a QCOW2 to RAW this morning because the VM kept slowing down. qemu-img never lets me down 😂