Hyper-V dynamic migration principles

To catch up with VMware virtualization overlord, Microsoft began to support dynamic migration between physical machines and virtual machines from Hyper-V 2.0. Dynamic migration may not have high requirements for laboratories, but it is a watershed for enterprises to achieve virtualization maturity.

Before getting started, you need to clarify a concept.

Dynamic Hyper-V Live Migration is not an unplanned downtime in the fault state.

This application scenario is only used for scheduled downtime such as upgrade and hardware replacement.

Dynamic migration steps:

• Recommended connection between source and target computers

• Transfer Virtual Machine configurations and device information

• Transfer VM memory

• Suspend pending) Source Vm and transfer status

• Recover the target Virtual Machine

1. Recommended connection between source and target computers

This part of the communication involves two WMI calls to the two dll in the group:

Clusres. dll

The basic network, storage, WINS, DHCP, and scripts of the Cluster Resource Management dll ..)

Vmclusres. dll

Virtual Machine Cluster Resource Management dll

Live Migration is essentially a way to implement a cluster.

The speed and efficiency of communication are related to the loads on the source and target servers.

When the load on the source or target server is too high, WMI fails to call clusres. dll.

This scenario occurs when the PRO calls Live Migration, and will cause step 1, namely suspending and suspending.) The source virtual machine is suspended and the transfer status becomes stuck, causing the virtual machine to be suspended for a long time.

The error message is as follows:

Error (12711)

The error [MSCluster_Resource.Name = "SCVMM XXX01 Configuration"] indicates that the element cannot be found, and the VMM cannot complete the WMI operation on HOST01.contoso.com.

Details (element not found (0x490 ))

Patches provided by Microsoft must be deployed on all nodes:

Http://support.microsoft.com/kb/974930

2. Transmit virtual machine configuration and device information

It is worth noting that this part is not the XML configuration file in the Virtual Machine directory, but the information in the registry.

The above two steps are to complete the migration preparation, inform the target server of the resources required by the virtual machine, and allocate the required resources.

Iii. Transfer VM memory

This part is the core technical part of migration. Whether it is VMware or Hyper-V for migration, it is unavoidable.

The so-called services for sales will not be disconnected, but it is a legend. Technically, the disconnection time is reduced from the second level to the millisecond level.

Let's describe the memory transfer process in detail:

1. Lock the memory of the Guest host and send the information of this Part to the target server.

2. the Guest Host continues to run, enabling a new memory partition in the Host to provide services for the Guest Host. Only the changed content is saved in this region.

3. The new memory partition will continue to be locked and transferred.

4. Repeat 2 ~ 3. Ensure that the memory difference between the original HOST server and the target HOST server is within a very small clock period until the memory transfer in operation 1 is completed.

4. Pause pending) Source Vm and transfer status

This part contains three operations:

1. Mount the origin VM

2. Transfer the final source VM memory change segment

3. Notification storage: mount the storage to the target server

Step 4 is the key to the migration time consumption.

The key is to save the real-time memory status.

In Hyper-V 1.0, Quick Migration adopts the method of mounting the origin Vm and then processing the memory.

Therefore, during the migration process, we will find that the downtime is proportional to the amount of memory consumed by the virtual machine.

In Live Migration, downtime is no longer determined by the memory consumed by the migrated virtual machine.

Memory size is a relatively small memory segment that determines the downtime.

According to the actual test, in the Live Migration operation, the packet loss rate of ping packet monitoring varies by system load ~ Between 6.

It can fully meet the high availability requirements of general enterprises.

5. Restore the target Virtual Machine

This part is the same as normal restoration. No detailed description is provided.