= Features/Virt Device Failover = https://fedoraproject.org/wiki/Features/Virt_Device_Failover Feature owner(s): Michael S. Tsirkin <mst@xxxxxxxxxx>, Gal Hammer <hammer@xxxxxxxxxx>, Cole Robinson <crobinso@xxxxxxxxxx>, Laine Stump <laine@xxxxxxxxxx> Support for transparent failover between an assigned and an emulated device, allows enabling the migration and overcommit dynamically, while still gaining the performance benefits of device assignment and without disrupting the guest operation. == Detailed description == For virtual machines, device assignment is the best option for performance. However, when a device is assigned to a VM, both migration and memory overcommit are currently disabled. This feature aims at removing the performance/features tradeoff, by switching to an emulated device in a way that is almost transparent to users, for configurations where both host and guest are Fedora. Fedora should detect that the emulated device serves as a failover for the assigned device. When requested by the hypervisor, it will stop and eject the assigned device, switching to failover. After this point, migration and memory overcommit are possible, while device configuration is preserved. Once e.g. migration completes, the reverse switch can take place. Thus the device is controlled by: * before migration: device specific driver loaded in guest * during migration: driver loaded in host, virtio or emulated device driver loaded in guest * after migration: device specific driver loaded in guest At the kernel level, for networking, this can be done by and creating a bond in a failover configuration, and for storage, using multipath, on top of both the assigned and the emulated device. _______________________________________________ devel-announce mailing list devel-announce@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel-announce -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
