Functionality Upon delving a bit deeper into vMotion one must admit that the functionality is both simple and ingenious. Figure 3: The vMotion procedure from the point of view of the virtual machine The first step is to ensure that the source VM can be operated on the chosen destination server.
Then a second VM process is started on the target system and the resources are reserved. Next a system memory checkpoint is created. This means all changes to the source VM are written to an extra memory area. The contents of the system memory recorded at the checkpoint are transferred to the target VM.
The last modifications to the main memory are transferred to the target VM in milliseconds. The vMotion process is ended and a reverse ARP packet is sent to the physical switch important: Notify Switches must be activated in the properties of the virtual switch. Hard disk access is taken over by the target ESX. The source VM is shut down. One additional comment about what the vMotion checkpoints record: all devices and their status CPU registers main memory contents a serialization of the status for transmission over the network As you can see vMotion is concerned mostly with the transfer of the main memory contents from one ESX server to another, with a final notification telling the physical network about the new interface over which the VM is reachable sent once the process is finished.
The following table shows an example how the memory transfer can be computed. Pre-Copy Iteration Main memory to be transferred Time needed for the transfer Change in memory during the transfer 1 2. Read The Blog. Monitor and Analyze Performance and Log files:. Performance monitoring for your systems and applications with log analysis tamperproof using immudb and license compliance RedHat, Oracle, SAP and more in one virtual appliance!
Discover Metrics and Logs. Subscribe to Our Newsletter. Get the latest product updates, company news, and special offers delivered right to your inbox. Share on twitter. Share on linkedin. Our product offers a set of tools to let you protect your VMware-based infrastructure. These include VM Replication and Site Recovery, features that can help you handle the process of data center migration.
You can create a replica, i. You can perform live migration of your VMs from one physical host to another, without any downtime. This technology allows the VM processes to keep running throughout the migration process.
Simply for reference, VMware supports cold migration mode, too, which means that migration can be performed when the VM is turned off or suspended.
As live migration is performed, the VM retains its current memory content, network identity and connections, and all additional information that defines it.
On a gigabit Ethernet network, the process of migration takes less than two seconds, according to VMware documentation. To reduce the need for manual effort, you can automate and schedule the migration of your VMs. The migration details can be set up via the Migrate Virtual Machine wizard. Depending on your needs, you can schedule the migration process to run either once or multiple times.
Additionally, VMware vMotion can help you find an appropriate destination host within seconds, thus eliminating the need to do this manually. If you are running a large infrastructure that spans across multiple locations or countries, VMware offers functionality for migrating VMs over large distances. Available since the vSphere 6. RTT, or round-trip time, is the length of time required for a signal or data packet to travel from a starting point to its destination and back again.
With VMware vMotion, this is about milliseconds or less. The RTT has been increased by almost 10 times, which means you can easily perform migration of live workloads between datacenters located on different continents. If you prefer to change the host and the datastore, both the state of the VM and the virtual disk are moved.
Migration can be performed between hosts, clusters, or data centers without shared storage. This functionality, officially known as Storage vMotion, allows you to simplify the maintenance and upgrading of your VMs, optimize disks for performance, or convert disk types.
Posted by Mike Murray Blog , Learning. You have to admit that VMWare created some really cool technology back in when they released VMotion. I still routinely run into people who have no idea that VMotion exists, and when they find out what it does they are always amazed that such a feat is even possible, much less practical! There are some amazing benefits to VMotion and Live Migration. Since a server can be moved to completely different hardware while it is running, without downtime the underlying hardware can be swapped out, or taken down for maintenance without the end-users or other applications being affected, or even knowing it has happened.
This has really changed how we handle system maintenance and outages in modern compute environments. Before this technology became commonplace in data centers, outage windows had to be negotiated with customers and servers had to be taken off-line for hours to replace or upgrade hardware.
In the VMotion world, new hardware can be built and the virtual server moved without any downtime. So how does VMotion work? Unlike your standard desktop or standard physical server, the hard disk of a VMWare server is not generally located on a physical disk inside the server.
While there are other technologies that VMWare can use VSAN, Hyper-Converged computing, or even storage migration , we are going to focus on this most common configuration. These physical servers all work together to share read-write access to this virtual hard drive. That alone is a pretty amazing feat when you think about the logistics of it!
This ghost is just a shell which will receive the memory contents next. The next big piece of understanding how VMotion works is related to the memory management within VMWare. VMotion takes a snapshot of the system RAM, a copy if you will, and starts the rapid transfer of this memory over the Ethernet network to the chosen host computer.
This includes the states of other system buffers, and even the video RAM.
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