After changes to the perpetual licensing scheme due to the acquisition of VMware by Broadcom in 2023, companies sought ways to migrate their workloads away from vSphere and onto open source or less risky platforms. Despite this, VMware has been one of the leading companies that provides solutions for virtual machine management and virtualization.
This article provides information on how VMware migration works internally and practical examples of migrating ESXi-based virtual machines onto an external solution like OpenStack via KVM and Kubevirt. This article does not discuss the steps for creating a virtualized environment, so it is best to have a testing or laboratory environment ready that uses VMware while following this article.
Summary of key VMware migration types
| VMware migration type | Description |
| vMotion (Hot Migration) | This method moves a running virtual machine between physical hosts without any downtime. It requires that the source and destination hosts share storage. |
| Storage vMotion (hot storage migration) | This approach transfers a virtual machine’s storage during a live migration, also without downtime. It is primarily used to move a VM to a host that doesn’t share storage with the source, such as between clusters. |
| Cold migration | Cold migration involves powering down the VM before moving it to another host or datastore. It is suitable when hot migration isn’t possible, like when the vMotion network is disconnected or the host architectures are different (e.g., Intel vs. AMD). |
| Cross vCenter vMotion | This migration type allows migrating VMs between different vCenter Server instances. It supports both shared and non-shared storage to help balance workloads across data centers or environments. |
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Introduction to VMware virtual machines
VMware’s virtual machine (VM) dates back to 1999, when VMware Workstations was its debut product, and the format of this machine has not changed dramatically since then. VMware encapsulates hardware and states into several files, which are what must be ported to migrate the VM to another platform. The table below summarizes these files.
| File | Description |
| -flat.vmdk | A disk file containing the VM data and/or operating system |
| .vmdk | A metadata descriptor file that describes disk size, type, and geometry |
| .vmx | A config file that describes items such as the VM’s name, OS, MAC address, and hardware |
| .vmem | A copy of a VM’s memory used for snapshots |
Please note that not all VMware files have been included in this list; you can view more in Broadcom’s official documentation.
VMware migration types
VMware provides several proprietary migration techniques to meet particular operational requirements, which can then cater to multiple situations. Here are some of the essential migration methods that can be performed within the VMware environment.
Note that the four migration techniques presented aren’t the only migration methods offered by VMware. For example, some organizations have infrastructure running on a cloud or a hybrid setup, and VMware has new modern technologies that cater to that situation.
vMotion
vMotion (or hot migration) enables the live migration of a running virtual machine from one physical host to another without downtime. The virtual machine’s memory status, open network connections, and CPU context are all smoothly transported. The VM’s memory pages are copied iteratively from the source to the destination host while the VM continues to run. A final “stun” phase, typically lasting milliseconds, occurs where any remaining changed memory pages are transferred, and the VM’s execution is then resumed on the destination host.
This migration technique is considered ideal when the source and destination hosts share storage.
The long history of VMware vMotion (source)
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Storage vMotion
Storage vMotion (or svMotion) is another hot migration method. The only difference between this and vMotion is that the storage is included during the move. This approach is commonly used when a VM needs to be moved to another host that does not have shared storage with the source, such as a cluster-to-cluster move, or for balancing storage I/O and utilization.
Cold migration
Cold migration involves transferring a virtual machine to another host or datastore after the VM has been powered down. Due to infrastructure limitations, this method suits scenarios where hot migration is unavailable or the vMotion network is disconnected between locations. An example use case is migrating between vCenters without connection to the vMotion network; another is when the destination host’s architecture differs from the source host’s (Intel vs. AMD).
Cross vCenter vMotion
Cross vCenter vMotion enables the migration of VMs between different vCenter Server instances. This is a significant advancement as it allows for broader workload mobility. Technically, it supports migrations where storage is either shared or not shared between the source and destination vCenters. The feature is primarily used for balancing workloads across disparate data centers or environments, facilitating data center consolidation and hybrid cloud strategies.
Advantages and Disadvantages of the Four Migration Types
Here is a summary of each migration technique’s advantages and disadvantages.
Migration Type | Pros | Cons |
vMotion |
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Storage vMotion |
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Cold Migration |
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Cross vCenter vMotion |
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OpenStack
OpenStack is a set of tools that allows the provisioning of virtual machines using an infrastructure-as-a-service (IaaS) methodology. OpenStack launched in 2010; it was initially a collaborative affair between NASA and Rackspace. Other tech companies such as IBM, Red Hat, and HP soon joined, and OpenStack Foundation became its own thing, eventually becoming part of the Open Infra Foundation (OIF) in 2021.
Organizations seeking to move away from expensive products can use the freedom of OpenStack’s open-source licensing to build cloud infrastructure. OpenStack supports a variety of Hypervisors such as KVM, Xen, LXC, and so on. Here are its essential components and their functions:
- Nova: VM management and deployment
- Cellometer: Monitoring and billing
- Neutron: Software-defined networking
- Cinder: Block storage service
OpenStack as an alternative to VMware
OpenStack functions as a fully open cloud platform, inheriting all the characteristics expected of cloud environments, such as on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service. It’s free from licensing and vendor lock-in since it uses the Apache 2.0 license. This means it’s a great alternative to products such as those from VMware by Broadcom, albeit at the cost of a steep learning curve and need for in-house support.
Simplified OpenStack architecture (source)
One of the key considerations when migrating from VMware to OpenStack is understanding how network virtualization differs between the two platforms. While VMware uses NSX for software-defined networking, OpenStack’s Neutron component relies on Open vSwitch (OVS) and Open Virtual Network (OVN) to provide similar capabilities.
Understanding these components is key, as you’ll need to map your existing VMware NSX configurations to OVN’s distributed architecture. The transition from NSX’s centralized approach to OVN’s distributed control plane can actually provide better scalability and fault tolerance for organizations operating at scale.
The following table describes how VMware differs from other solutions in terms of functions, advantages, and disadvantages.
| Function | VMware | Advantages | Disadvantages | Alternative |
| VM environment and management | vSphere | Widely adopted and has strong enterprise support | High licensing costs and vendor lock-in | OpenStack Compute (Nova) |
| Software-defined storage | vSAN | Simplifies storage management with tight vSphere integration | Requires compatible hardware and has a high entry cost | Ceph |
| Software-defined networking | NSX | Provides granular security and advanced networking features | Complex to deploy and manage for small teams | Neutron |
| IaaS | Vrealize Automation | Offers robust automation and lifecycle management tools. | Steep learning curve and resource-intensive to maintain | OpenStack Heat |
OpenStack migration tools
There are many options to convert a virtual machine from one platform to another, and the process is not always straightforward. Care should be taken to choose an appropriate method based on expertise, degree of required automation, downtime, data consistency, and the scale of your migration project.
Tools are free, CLI-based open source utilities and GUI-based enterprise solutions. Options include:
- Virt-V2V: A Red-Hat CLI-driven tool that ports VMs to KVM offline
- Coriolis: An enterprise-grade (licensed), live migration tool with multi-hypervisor support
- Hystax Acura: An enterprise-grade (licensed) automated, multi-cloud, and multi-hypervisor tool
- Trilio: A VMware migration tool native to OpenStack, scalable out of the box, and built into the OpenStack Horizon dashboard with cold and warm migration options
Migrating VMware to OpenStack
OpenStack is a good target platform for hybrid or entirely cloud-native deployments since it supports virtual machines (VMs) and containerized workloads. Workload migrations from VMware to OpenStack demonstrate a strategic move toward more operational freedom and an open-source architecture. Through this technique, businesses may embrace cloud-native technology at their own speed, cut license expenses, and prevent vendor lock-in.
A successful cross-solution migration requires carefully assessing key infrastructure components like workload compatibility, network architecture, and storage dependencies. In addition, industry standards and best practices must be followed when performing large migration activities, including running test migrations, load balancing during transition phases, using automation or a solution to reduce manual intervention, and having a backup available for migrating workloads.
Trilio’s VMware-OpenStack migration process (source)
OpenStack can run migrated VMs through supported hypervisors like KVM, and it can also integrate natively with Kubernetes through its wide array of components, enabling the orchestration and management of workloads across distributed environments. Organizations migrating from VMware often leverage this integration to modernize legacy applications into containerized services during or after migration.
Migrating VMs from VMware to OpenStack
Workloads, specifically virtual machines, are usually exported from VMware and then deployed into OpenStack as part of the migration process. Prior to this section, we presented multiple tools you can leverage to handle OpenStack migration from VMware.
Migration solutions like Trilio can be seamlessly integrated into live production clouds without disrupting ongoing operations, making your migration seamless and effective. A seamless integration means that the migration process doesn’t require extensive pre-migration downtime, application freezes, or complex manual cutovers that risk breaking existing services. Instead, Trilio can operate “in-band,” working alongside your existing infrastructure. It achieves this by often leveraging mechanisms like warm migration or live snapshots, where data is continuously replicated from the source (VMware VMs) to the target (OpenStack VMs) while the original workloads remain active and accessible to users.
Trilio’s VMware-OpenStack architecture (source)
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Conclusion
VMware has long been a standard for managing VMs, but VMware’s enterprise licenses are on the pricier side, so you may consider looking into other solutions. OpenStack as a platform is one good example, as it provides an open-sourced virtualization alternative for running your virtual machines and containerized workloads on another platform.
When transferring your workloads from VMware to OpenStack, you must be as prepared as possible to avoid disruptions to your service. This is a good reason to look for solutions that effectively integrate these two systems. One of these solutions is Trilio, which delivers tenant-driven workflows to discover VMware workloads and extract their data and associated metadata. Trilio creates these resources on the OpenStack platform, then gives users maximum flexibility to remap VMware constructs to OpenStack constructs.
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