[libvirt] [Block Replication] Question about supporting COLO in libvirt
Hi, I'm trying to implement supporting COLO in libvirt, But i found an annoying problem that libvirt does not support the command line option argument syntax we used for block replication in QEMU. That is libvirt does not support the bellow syntax for block: -drive driver=qcow2,file.filename=test:a.qcow2 -drive file=test.qcow2,\ backing.file.filename=/dev/fdset/1 It seems to be a new syntax that libvirt does not support thought it has been exist in QEMU for a time. I found some introductions from http://www.linux-kvm.org/images/3/34/Kvm-forum-2013-block-dev-configuration.... The command line we use for COLO is just like the above syntax, For example, for the shared disk in COLO, it is: -drive if=none,driver=qcow2,file.filename=/mnt/ramfs/hidden_disk.img,id=hidden_disk0,\ backing.driver=raw,backing.file.filename=1.raw \ -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\ file.driver=qcow2,top-id=active-disk0,\ file.file.filename=/mnt/ramfs/active_disk.img,\ file.backing=hidden_disk0,shared-disk=on For the none-shared disk in COLO, it is quite same with the shared-disk: -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \ -drive if=xxx,id=topxxx,driver=replication,mode=secondary,top-id=topxxx\ file.file.filename=active_disk.qcow2,\ file.driver=qcow2,\ file.backing.file.filename=hidden_disk.qcow2,\ file.backing.driver=qcow2,\ file.backing.backing=colo1 So there seems to be two ways to solve this problem. One is to support this new option argument syntax in libvirt, but I'm not sure if it is difficult or not to implement it, and i don't know where to start either. Another way is to convert these command line options in QEMU totally, I mean hidden the descriptions of 'active_disk' and 'hidden_disk' disks. Create/add them dynamicly by qmp commands while users want to make VM goes into COLO state. That's just like to support live image clone in QEMU. Any ideas ? Thanks, Hailiang
On Mon, Feb 06, 2017 at 08:34:28PM +0800, Hailiang Zhang wrote:
Hi, I'm trying to implement supporting COLO in libvirt, But i found an annoying problem that libvirt does not support the command line option argument syntax we used for block replication in QEMU.
That is libvirt does not support the bellow syntax for block: -drive driver=qcow2,file.filename=test:a.qcow2 -drive file=test.qcow2,\ backing.file.filename=/dev/fdset/1
It seems to be a new syntax that libvirt does not support thought it has been exist in QEMU for a time. I found some introductions from http://www.linux-kvm.org/images/3/34/Kvm-forum-2013-block-dev-configuration....
The command line we use for COLO is just like the above syntax, For example, for the shared disk in COLO, it is: -drive if=none,driver=qcow2,file.filename=/mnt/ramfs/hidden_disk.img,id=hidden_disk0,\ backing.driver=raw,backing.file.filename=1.raw \ -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\ file.driver=qcow2,top-id=active-disk0,\ file.file.filename=/mnt/ramfs/active_disk.img,\ file.backing=hidden_disk0,shared-disk=on
For the none-shared disk in COLO, it is quite same with the shared-disk: -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \ -drive if=xxx,id=topxxx,driver=replication,mode=secondary,top-id=topxxx\ file.file.filename=active_disk.qcow2,\ file.driver=qcow2,\ file.backing.file.filename=hidden_disk.qcow2,\ file.backing.driver=qcow2,\ file.backing.backing=colo1
So there seems to be two ways to solve this problem.
One is to support this new option argument syntax in libvirt, but I'm not sure if it is difficult or not to implement it, and i don't know where to start either.
Libvirt has to start supporting this new syntax. It is required for many different use cases beyond just colo. For example, to be able to explicitly given qemu details about a backing file format to remove probing, or to be able to set LUKS passwords on backing files, and more beside Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|
On 2017/2/6 20:39, Daniel P. Berrange wrote:
On Mon, Feb 06, 2017 at 08:34:28PM +0800, Hailiang Zhang wrote:
Hi, I'm trying to implement supporting COLO in libvirt, But i found an annoying problem that libvirt does not support the command line option argument syntax we used for block replication in QEMU.
That is libvirt does not support the bellow syntax for block: -drive driver=qcow2,file.filename=test:a.qcow2 -drive file=test.qcow2,\ backing.file.filename=/dev/fdset/1
It seems to be a new syntax that libvirt does not support thought it has been exist in QEMU for a time. I found some introductions from http://www.linux-kvm.org/images/3/34/Kvm-forum-2013-block-dev-configuration....
The command line we use for COLO is just like the above syntax, For example, for the shared disk in COLO, it is: -drive if=none,driver=qcow2,file.filename=/mnt/ramfs/hidden_disk.img,id=hidden_disk0,\ backing.driver=raw,backing.file.filename=1.raw \ -drive if=virtio,id=active-disk0,driver=replication,mode=secondary,\ file.driver=qcow2,top-id=active-disk0,\ file.file.filename=/mnt/ramfs/active_disk.img,\ file.backing=hidden_disk0,shared-disk=on
For the none-shared disk in COLO, it is quite same with the shared-disk: -drive if=none,driver=raw,file.filename=1.raw,id=colo1 \ -drive if=xxx,id=topxxx,driver=replication,mode=secondary,top-id=topxxx\ file.file.filename=active_disk.qcow2,\ file.driver=qcow2,\ file.backing.file.filename=hidden_disk.qcow2,\ file.backing.driver=qcow2,\ file.backing.backing=colo1
So there seems to be two ways to solve this problem.
One is to support this new option argument syntax in libvirt, but I'm not sure if it is difficult or not to implement it, and i don't know where to start either.
Libvirt has to start supporting this new syntax. It is required for many different use cases beyond just colo. For example, to be able to explicitly given qemu details about a backing file format to remove probing, or to be able to set LUKS passwords on backing files, and more beside
Thanks for your quick reply, do you or other developers in libvirt have plan to implement it ? Thanks, Hailiang
Regards, Daniel
participants (2)
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Daniel P. Berrange -
Hailiang Zhang