VM Live Migration

As the digitization of businesses expands, companies need to migrate from the conventional methods of server management to virtualization. Virtual machines offer more flexibility, scalability, and cost-effective server management. However, some challenges come with virtual machines. These challenges include continuous backups and upgrades, which sometimes require temporary movement of the virtual machines.

While this might be arduous for businesses due to the fear of user disruption, live migration has made this transition relatively safe and easy. Live migration of virtual machines makes it possible to move virtual machines with minimal downtime. This feature allows you to make changes and upgrades to your infrastructure without interrupting your users. However, this process involves several steps that you must understand to avoid unintended results. Therefore, this post will briefly discuss the live migration process and how it works. Then, we will discuss some advanced features of live migration.

Overview of Live Migration

Live migration of virtual machines (VMs) is a process that allows for the seamless relocation of virtual machines from one physical server to another without service disruption. You can employ this process while planning server maintenance, disaster recovery, and server-side performance optimization. However, a basic knowledge of virtualization and how it operates is essential to understand live migration.

Virtualization is a technology that enables one physical server to run multiple operating systems and multiple applications simultaneously without requiring various physical servers. Each virtualized operating system and application runs as a “virtual machine” (VM). A VM is a software container containing the OS, applications, and data that make up the virtualized environment.

Live migration allows for the migration of virthines without shutting them down, allowing for near-seamless service continuity. This ability will enable you to move VMs effortlessly from one physical host to another without impacting services, making it easier to manage and maintain the virtual environment. Now, let’s look at how the live migration of virtual machines works.

How Does Live Migration Work?

Live migration is a powerful tool for your business when you need to move VMs between physical hosts quickly and without interruption in service. The process requires that the source and target hosts run the same virtualization software, are connected to the same network, and have access to the same storage system. Additionally, the target host must have enough resources to support the VM. Once these pre-conditions are met, the steps involved in live migration include preparing the source host and transferring the VM image. Then, booting up the VM image, sharing the memory and CPU state, and cleaning up the source host.

Prerequisites for Live Migration

Live migration requires both the source and destination servers to meet specific criteria for it to work. The requirements of live migration are:

  • The source and destination servers must be running the same version of the hypervisor. A hypervisor is a program that creates and runs virtual machines on a physical server.
  • Both the source and destination servers must have the same hardware configuration. This requirement means that the same number of CPUs, memory, storage, and network cards must be present on both servers.
  • Both the source and destination servers must have access to the same storage system. This requirement could be a shared storage system such as a SAN (storage area network) or a local storage system such as an internal hard drive.
  • Both the source and destination servers must connect to the same network. This requirement means that the same network switches and routers must be on both servers.

Steps Involved in Live Migration

Once the requirements for live migration are reached, the following steps are required for the process to be successful:

  • The first step in live migration is to prepare the source host. This step requires shutting down the VMs, and storing the image of the VM must on the target host’s storage system. Once done, the source host transfers the VM image to the target host.
  • The next step is for the target host to begin booting up the VM image. This process involves the virtualization software, which creates the necessary environment for the VM to run.
  • Once the VM is running, the target host will begin transferring the memory and CPU state of the VM from the source host.
  • Finally, the target host will begin cleaning up the source host. This step involves the virtualization software, which deletes the VM image from the source host’s storage system.
  • Once achieved, the live migration process is complete, and the VM runs on the target host.

What are the Requirements for a Successful Live Migration?

Live migration is one of the most efficient ways to move workloads from one server to another without interruption. A few crucial elements should be in place to ensure a successful live migration.

Infrastructure Setup

The first aspect of a successful live migration is the infrastructure setup. This step ensures that the physical hardware required for the migration is in place and ready to go. It includes the server, storage, and networking equipment needed for the migration. Also, it involves ensuring adequate installation and configuration of the server operating system and any other software required for the migration.

Network and Security Setup

The second part of the live migration process is the network and security setup. This step involves creating networks and virtual networks required for the live migration. It also involves setting up access control and security policies to ensure that the network is secure and can handle the load of the live migration. However, It is important to remember that the completion of this process should come before the actual migration begins.

Software and Tools Setup

The last part of the live migration process is the setup of the software and tools needed for the migration. This step includes the software used to facilitate the migration process. It also includes any tools used to monitor and troubleshoot the migration process. These tools must be appropriately set up and tested before the migration begins.

Common Challenges of Live Migration

Migrating to a live environment has become a commonplace practice for businesses nowadays. However, it has its challenges. To help you understand the common issues associated with live migration, we’ll discuss three of the most common challenges: performance, network bandwidth limitations, and security risks.

Performance Issues

Performance can be a significant issue when using live migration. For instance, a lack of resources or high latency can affect the quality of the user experience. Additionally, incompatibility between the hardware or software of the source and target machines can lead to slow performance. As a result, ensuring that all components are compatible before attempting a live migration is vital.

Network Bandwidth Limitations

Live migration can also be affected by limited bandwidth. In other words, if your network is too sluggish to support the transfer, the migration will take longer than expected. Additionally, if your network is congested, it can lead to a slower connection and a longer migration time. To avoid this issue, ensure you have a network that can handle the traffic associated with live migration.

Security Risks

Security is another crucial consideration during live migration. In an enterprise environment, ensuring the security of the data transferred is vital. If the data is intercepted or accessed by unauthorized users, it can lead to a data breach. Minimizing the threat of a security breach is essential, so ensure both the source and destination systems have appropriate security protocols. Additionally, ensure that your data encryption is optimal during the transfer process. However, before live migration, it is essential to consider all relevant factors to ensure a successful migration.

Advanced Features of Live Migration

Live migration offers a series of features that enable a smooth migration experience for your VMs. Live migration has two main categories – Live Storage Migration and Live Network Migration.

Live Storage Migration

Live Storage Migration allows you to move the virtual disks associated with running your VMs from one storage subsystem to another without any service interruption. This feature is handy for large-scale migrations of VMs to different storage devices, such as when expanding capacity or deploying new storage systems. Live Storage Migration ensures that the data remains consistent throughout the migration process, minimizing the risk of data corruption or lost files.

Live Network Migration

Live Network Migration is another advanced feature of Live Migration that enables you to move a running VM from one physical host to another via the network. This feature eliminates the need for physical cable connections and allows for more efficient resource utilization. Live Network Migration also helps ensure that the VM remains running and connected to the network throughout the migration process. Live Storage Migration and Live Network Migration are potent features of Live Migration that allow for greater flexibility and resource utilization. You can use these features to easily and quickly move VMs between physical hosts with minimal downtime and without service interruption.

Future Outlook of Live Migration

Live migration is an effective and efficient way to move your virtual machines from one physical server to another without downtime or interruption in service. It also provides numerous benefits, such as improved scalability, better resource utilization, increased availability, and reduced downtime. Despite these fantastic benefits, there are still challenges to  using live mitigation processes for migrating your VMs. You must avoid or reduce these risks to a bare minimum for efficient outputs.

Finally, live migration’s future looks bright as more organizations take advantage of this technology. With exemplary implementation and management, Live Migration can be a powerful tool to help you maximize your IT infrastructure performance.

Paweł Mączka Photo

text written by:

Pawel Maczka, CTO at Storware