Jonah Patel
Live migration is the process of moving a virtual machine (VM) from one host to another without interrupting access to the VM. The time between suspending the old VM and starting the new one is brief, making it possible to avoid service interruptions during migrations. Live migration is considered a major step in virtualization. It involves the transfer of VM memory, network connectivity, and storage to a new destination within the cluster. There are various techniques for live VM migration, such as pre-copy, post-copy, and hybrid methods, each with its advantages and trade-offs. Live migration offers several benefits, including efficient load balancing, fault tolerance, energy efficiency, and security. It also allows for low-disruption fault management and system maintenance. Live migration supports migrating an entire OS and its applications as one unit, eliminating difficulties in process-level migration.
| Characteristics | Values |
|---|---|
| Live migration | Moving a virtual machine (VM) from one host to another without interrupting access to the VM |
| Live migration process | Transfer of VM memory, network connectivity, and storage to a new destination within the cluster |
| Live migration types | Pre-copy, post-copy, and hybrid techniques |
| Live migration tools | Red Hat OpenShift Virtualization, VMware vSphere vMotion, Hyper-V from Microsoft Windows Server, Nutanix |
| Live migration benefits | Load balancing, fault tolerance, energy efficiency, power management, security, low-disruption fault management, system maintenance |
| Live migration challenges | Network contention, migration latency, performance degradation, increased migration time, service delay, SLA violation |
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What You'll Learn
Live migration's benefits for data centre and cluster administrators
Live migration is the process of moving a virtual machine (VM) from one host to another without interrupting access to the VM. This process offers several benefits for data centre and cluster administrators.
Firstly, live migration eliminates the difficulties associated with process-level migration. By migrating an entire operating system (OS) and its applications as a single unit, issues of residual dependencies are removed, as the original host machine no longer needs to remain available to service memory accesses or system calls. This allows for the consistent and efficient transfer of the VM's in-memory state, including both the kernel internal state and application-level state.
Secondly, live migration enables more efficient load balancing. Systems and CPU resources can be shared for optimum use, and administrators can rearrange OS instances across machines in a cluster to relieve load. This helps improve VM capacity and network performance.
Thirdly, live migration allows applications to continue running while administrators perform maintenance activities, such as security updates, in the background. This ensures that maintenance can be carried out without disrupting normal operations or causing downtime for end users.
Additionally, live migration can be used to increase resources for VM workloads. Administrators can easily add new hosts to a Hyper-V cluster, providing instant resource scalability. Live migration also helps save power and manage load in a cloud data centre, contributing to energy efficiency and cost savings.
Furthermore, live migration reduces downtime by using a pre-paging approach. The OS predicts which pages of memory will be required and pre-loads them into the main memory, avoiding the need to halt the VM during migration. This minimises adverse effects on the end user and ensures seamless service continuity.
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Live migration and virtual machine scheduling
Live migration is a process that moves a virtual machine (VM) from one host to another without interrupting access to the VM. It is a fundamental component of virtualization, allowing the migration of VMs from one location to another without suspending them. This process offers several benefits, such as load adjustment, online support, control, and proactive adaptation to internal failures. Live migration is used in situations like planned maintenance or balancing workload resources. It involves the transfer of VM memory, network connectivity, and storage to a new destination within the cluster.
The live migration process can be optimized using CPU scheduling. By controlling the CPU scheduler of the VM monitor, the speed of memory changes can be limited, improving migration liveness. This is particularly useful when there is a high memory writing speed or a slow pre-copy speed. Additionally, Binary Particle Swarm Optimization (BPSO) can be used to select host VMs based on multi-objective functions, including task transferring time, task execution time, and energy consumption.
Virtual machine scheduling plays a crucial role in live migration. It helps in load balancing by moving VMs to host machines with lower usage if their current host becomes overloaded or under-utilized. This improves VM capacity and network performance. VM scheduling can also minimize migration latency, especially during live VM migration across high-latency, low-bandwidth networks.
To achieve efficient load balancing, live migration allows the migration of an entire VM, including its operating system (OS) and applications, as one unit. This eliminates the issue of residual dependencies on the original host machine and ensures consistent and efficient transfer of the VM's in-memory state. Additionally, live migration supports low-disruption fault management and low-level system maintenance, making it a valuable tool for administrators of data centers and clusters.
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Live migration and energy efficiency
Live migration is the process of moving a virtual machine (VM) from one host to another without interrupting access to the VM. It is used in situations like planned maintenance or to balance workload resources. Live migration is considered a major step in virtualization, as it helps accommodate low-disruption fault management, load balancing, and low-level system maintenance.
Virtualization is an innovation widely utilized in modern data centers for cloud computing to achieve energy-efficient operations of servers. Virtual machine migration brings multiple benefits, such as resource distribution and energy-aware consolidation. Server consolidation enables multiple instances of operating systems to run simultaneously on a single machine, allowing for the consolidation of servers through VM live migration.
However, migration of virtual machines also brings extra energy consumption and security concerns. To address these challenges, researchers have proposed secure energy-aware provisioning of cloud computing resources on consolidated and virtualized platforms. One approach is the Energy-Aware Task Scheduling (EATS) algorithm, which assigns tasks to VMs where the increase in energy consumption is minimized, considering both active and idle VMs. This algorithm has been shown to achieve energy savings in a heterogeneous cloud-computing environment.
Another technique to improve energy efficiency during live migration is the pre-copy technique, which minimizes downtime by reducing the number of pages transferred and total migration time. Additionally, load balancing mechanisms can help achieve balanced utilization of resources, maximizing throughput, availability, and reliability, which can lead to improved energy efficiency.
Overall, live migration plays a crucial role in improving energy efficiency in data centers and cloud computing environments by enabling the dynamic distribution of resources, consolidating servers, and minimizing downtime during maintenance and updates.
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Live migration and load balancing
Live migration is the process of moving a virtual machine (VM) from one physical host to another without interrupting access to the VM or causing any downtime. It is used in situations like planned maintenance or to balance workload resources. Live migration is a major step in virtualization, helping accommodate low-disruption fault management, load balancing, and low-level system maintenance.
Load balancing is one of the main challenges in a VM environment, ensuring equal utilization of all available resources while avoiding overloading a subset of machines. Live migration supports more efficient load balancing, allowing systems and CPU resources to be shared for optimum use. It also enables applications to continue running while the administrator manages maintenance activities, such as security updates, in the background.
Live migration of VMs can be achieved by migrating from high-load machines to light-load ones. This can be done dynamically, based on resource usage, or through a load-balancing policy. For example, a Red Hat Virtualization environment uses load balancing policies to respond to changes in demand for host resources, ensuring that no single host in a cluster is responsible for all the VMs and recognizing underutilized hosts to migrate VMs off of them.
There are various techniques for live VM migration, including pre-copy, post-copy, and hybrid methods. The pre-copy technique aims to minimize downtime by reducing the transferred VM's state, ensuring seamless transfer without interrupting the application service. On the other hand, the post-copy technique transfers all memory pages at most once, reducing network page faults, but it has more downtime due to migration latency. Hybrid methods combine VM replication with VM scheduling, using de-duplication methods to address the additional storage requirements generated by the increasing number of VM image replicas.
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Live migration and fault management
Live migration is the process of moving a virtual machine (VM) from one host to another without interrupting access to the VM. It is a powerful tool for data centre administrators, allowing them to perform hardware maintenance, load balancing, fault management, resource sharing, and low-level system maintenance without disrupting normal operations or causing downtime.
Live migration is often used when maintenance or updates are required on the physical host machine. It allows an entire VM, including its operating system (OS) and applications, to be moved as one unit to a new host. This eliminates the issue of residual dependencies on the original host and ensures the VM's in-memory state can be transferred consistently and efficiently. Live migration also helps to accommodate low-disruption fault management. If a system crashes, live migration can minimise downtime by using a pre-paging approach, where the OS predicts which pages of memory will be required and pre-loads them into the main memory, allowing the VM to continue running.
There are several steps to the live migration process. Firstly, an initial preparation phase is essential to ensure a smooth migration. This involves a technical assessment of the target host to ensure it has sufficient resources, including CPU capacity, memory, and storage space, to support the incoming VM without overcommitting its resources and causing performance degradation. Once the target host has been selected, the data in the VM's memory is transferred to it. An "operational resource state" is then created on the target machine, consisting of CPU, memory, and storage. The original VM is then suspended, copied, and initiated on the destination host.
To ensure the long-term stability and performance of the VM in its new environment, continuous monitoring is crucial even after the migration is complete. Documenting the migration process, including details such as duration, data transferred, and any challenges encountered, can also help improve future migration processes.
Live migration offers several benefits, including boosting energy efficiency, enabling proactive performance management and maintenance, improving disaster recovery, and enhancing network load balancing. It allows for better resource utilisation, ensuring VMs run on the most suitable hardware, and enhances application availability. It also provides flexibility in scheduling maintenance, reduces the risk of data loss, and simplifies routine maintenance and system updates.
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Frequently asked questions
Live migration is the process of moving a virtual machine (VM) from one host to another without interrupting access to the VM.
Live migration offers several benefits. It eliminates the issue of residual dependencies that require the original host machine to remain available. It also supports more efficient load balancing, so systems and CPU resources can be shared for optimum use. Live migration also allows applications to continue running while the administrator manages maintenance activities, such as security updates, in the background.
Live migration can lead to performance degradation. It is also difficult for cloud providers to provide requested resources to end users in a timely fashion. Live migration of virtual machines with high latency and low bandwidth is also challenging.
The live migration process starts by transferring the data in the VM's memory to the target physical machine. Once all the data is transferred, an "operational resource state" consisting of CPU, memory and storage is created on the target machine. After this, the original VM is suspended, copied, and initiated on the destination.
