Dm-qcow2: qcow2 as Device-mapper Block Device - Aleksandr Mikhalitsyn & Denis V. Lunev, Virtuozzo
Dm-qcow2: qcow2 as Device-mapper Block Device - Aleksandr Mikhalitsyn & Denis V. Lunev, Virtuozzo
Most of container runtimes provides containers rootfs using host fs bindmounts, layered fs (overlayfs, aufs) or using a loop device. OpenVZ 7 uses special custom format ploop (Parallels loop) which more feature-rich and allows IO freeze, snapshots, backups. On the VM planet there is QCOW2 format. A new dm-qcow2 driver [1] developed by Kirill Tkhai (Virtuozzo) allows to utilize this format for the containers. This talk will cover main topic parts briefly: Intro and motivation. - Why loop is not ideal for the system containers? - Why in the kernel? - Why device mapper? - How it works on practice? (Example or demo) Tech details - Generic design. How IO requests are handled - Application to snapshots/backups Discussion - Integration with LXC? - Performance benefits for Qemu (vhost integration) [1] dm: Introduce dm-qcow2 driver to attach QCOW2 files as block device https://lore.kernel.org/all/164846619...