R&D/Hypervisor

QCOW2 analysis

sunshout 2014. 8. 21. 22:10

sunshout2@choonho:~/opensource/qemu$ qemu-img create -f qcow2 a.img 1G

Formatting 'a.img', fmt=qcow2 size=1073741824 encryption=off cluster_size=65536 lazy_refcounts=off


sunshout2@choonho:~/opensource/qemu$ qemu-img info a.img

image: a.img

file format: qcow2

virtual size: 1.0G (1073741824 bytes)

disk size: 196K

cluster_size: 65536

Format specific information:

    compat: 1.1

    lazy refcounts: false



빈 qcow2 디스크를 생성하면 3개의 cluster로 구성된 파일이 생성된다.


img_create call sequence




Qcow2 Disk layout




QCOW2Cache









참조: 

https://people.gnome.org/~markmc/qcow-image-format.html

qcow2 => http://www.linux-kvm.org/wiki/images/6/63/2011-forum-qcow2.pdf

FVD: a High-Performace Virtual Machine Image Format for Cloud, Usenix ATC11

 - https://www.usenix.org/legacy/event/atc11/tech/final_files/Tang.pdf