LWN: Comments on "Changed-block tracking and differential backups in QEMU"

Changed-block tracking and differential backups in QEMU

abii — Tue, 24 Aug 2021 10:22:10 +0000

hi,

yes, this is the more advanced version. I also have played with the push based model, here is another simple project:

Changed-block tracking and differential backups in QEMU

kashyap — Fri, 15 Jan 2021 14:30:23 +0000

Cool; reading the code, I see that you're using the pull-based mechanism to take the backup via the NBD export. And also handling the backup restoration aspects yourself—which is "required" by the pull-based approach, anyway. I also notice you're using the libvirt APIs.

Thanks for sharing!

Changed-block tracking and differential backups in QEMU

abii — Thu, 31 Dec 2020 09:23:11 +0000

I have created a small project on github that makes use of the new dirty bitmap features and
enables you to create live full/incremental backups for virtual machines running on libvirt/qemu
setups supporting the new features:

https://github.com/abbbi/virtnbdbackup

Changed-block tracking and differential backups in QEMU

kashyap — Fri, 20 Nov 2020 15:23:09 +0000

Very interesting; thanks for sharing. If you get time, might want to write a QEMU blog post[1] on your implementation approach—other users writing their own QEMU-based backup tooling might learn from your experience. :-)

[1] https://www.qemu.org/blog/

Changed-block tracking and differential backups in QEMU

tlamp — Thu, 19 Nov 2020 15:04:53 +0000

We used them to do fast and cheap backups on running machines for our new rust based open-source backup server[0], using a rust library with C bindings[1] to combine that with QEMU.

The code enabling dirty bitmap tracking was surprisingly small, a subset of it can be found at [2] (we really need to clean up the oot patches a bit).

We also use bitmaps in combination with ZFS sync to get a cheap and fast live migration even if bigger local storage is in use, as only the delta between the last synced snapshot needs to be moved, which can be tracked with those dirty bitmaps nicely.

[0]: https://pbs.proxmox.com/
[1]: https://git.proxmox.com/?p=proxmox-backup-qemu.git;a=tree
[2]: https://git.proxmox.com/?p=pve-qemu.git;a=blob;f=debian/p...