Shulou(Shulou.com)06/02 Report--

The migration of KVM virtual machines between different hosts is a complex problem. There are many solutions, but different solutions have their advantages and disadvantages. Let's analyze several available migration schemes of KVM virtual machines.

1. Data transfer during virtual machine migration (disk mirroring and memory data)

There are usually two common ways of data transmission:

-hypervisor-based transmission mechanism, that is, data transmission through the connection between host

-libvirtd-based transmission mechanism, that is, data transfer between two libvirtd processes

(1) data transmission based on hypervisor

This kind of transmission has the lowest overload because it transmits naked data and does not support data encryption. In addition, because it depends on the network of hypervisor, you need to make some specific configuration of hypervisor networks, such as opening some ports.

(2) data transmission based on libvirtd

This transmission mode supports encryption and transmits data through the built-in RPC protocol of libvirt, but the disadvantage is that in addition to transferring naked data, it also needs to transfer some additional data, which is a big problem for virtual machines with large mirror size. The advantage is that because it is not dependent on hypervisor network, there is no need for hypervisor to configure network too much, just open a specified port.

(2) Control flow during virtual machine migration

Direct migration with management, which is initiated by an administrative client, which completely controls the entire migration process, so it must be able and have permission to access the libvirtd on the source and destination hosts. Because there is an additional administrative client, there is no need for direct communication between the source libvirtd and the destination libvirtd, just follow the instructions of the administrative client. The advantages of this approach are:

If the client application crashes, or otherwise loses its connection to libvirtd during the migration process, an attempt will be made to abort the migration and restart the guest CPUs on the source host. There may be scenarios where this cannot be safely done, in which cases the guest will be left paused on one or both of the hosts

Point-to-point migration with management side, in which the management client interacts with the source libvirtd, and then the source libvirtd completely controls the entire migration process. The advantage is that even if the administrative client is down, the migration can be completed normally.

Http://blog.chinaunix.net/uid-20940095-id-3616577.html

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