COMPARISON · CHECKED 20 OCTOBER 2026
VMware to OpenStack migration tools, compared
Leaving vSphere for OpenStack starts with choosing how the VMs will move. Here are the tools teams evaluate, side by side, from each project's own documentation: what each moves, where to, whether the VM keeps running while its disks copy, and what happens around the cutover.
- Compared
- Seamless Migrate, MigrateKit, vJailbreak, Red Hat's VMware migration toolkit, os-migrate, Coriolis, virt-v2v
- Method
- Each project's own repository and documentation, read on 20 October 2026
- Common ground
- Every warm VMware path here uses Changed Block Tracking; most convert with virt-v2v
- Disclosure
- Written by the Seamless Migrate project; corrections welcome as issues
At a glance
- Documented
- Not available
- Not in its docs
| Tool | License | Interface | Sources | Destinations | Warm copy | Cutover control | Rollback |
|---|---|---|---|---|---|---|---|
| Seamless Migrate (opens in a new tab)This project0.4.0-rc.1, pre-release, October 2026 | Apache 2.0 | Dashboard, REST API with server-sent events, CLI | VMware vSphere 7.0U3 and 8.x (vCenter); RHOSP 17.1; community OpenStack, Queens and later | RHOSO 18.0, or community OpenStack 2023.1 Antelope to 2026.2 Hibiscus | Yes: CBT passes for VMware; a snapshot pre-copy for OpenStack sources | Yes: Waves with a pilot first; a change window, a second approver and a free slot for every cutover | Yes: Automatic after a failed verification, available until finalize |
| MigrateKit (opens in a new tab)VEXXHOSTNo tagged release; last code change September 2025 | Apache 2.0 | CLI in a Docker container, one VM per command | VMware vCenter, or an ESXi host that exposes the API | OpenStack | Yes: Repeated sync cycles with CBT while the VM runs, then a cutover command | Not in its docs: You run the cutover command when you choose | Not in its docs: Not in its docs |
| vJailbreak (opens in a new tab)Platform9v0.5.0, September 2026 | Business Source License 1.1 (source-available, free to use); each version becomes MPL 2.0 after four years | Web UI, Kubernetes resources, API | VMware vCenter 6.7, 7.0 and 8.0 | Platform9 Private Cloud Director or any OpenStack-compliant cloud; ESXi host conversion for Private Cloud Director only | Yes: Live copy with CBT, then power-off and cutover | Yes: Copy start time; cutover in a time window, right after the copy or when an admin triggers it | Not in its docs: Not in its docs |
| VMware migration toolkit (opens in a new tab)Red Hat; upstream os-migrate vmware-migration-kitv2.2.7, June 2026 | Apache 2.0 | Ansible collection, from the CLI or Ansible Automation Platform | VMware vCenter (7 and 8) and ESXi | RHOSO 18.0 in Red Hat's product; OpenStack upstream | Yes: CBT seeding while the VM runs, then a cutover run | Not in its docs: Parallel migrations per conversion host; the timing is up to you | No: Not in a release yet; rollback work merged on main in October 2026 |
| os-migrate (opens in a new tab)os-migrate project1.0.5, June 2026 | Apache 2.0 | Ansible collection | OpenStack only | OpenStack (its docs: versions 13 to 16 and 16 to 18) | No: Each source instance is shut off for its copy | Not in its docs: Batches by filter; idempotent re-runs | Not in its docs: Cleans up after a failure |
| Coriolis (opens in a new tab)Cloudbase SolutionsTag 1.3.5; no GitHub releases | Core under AGPL 3.0; migrations need a commercial per-VM licence | Web UI, REST API, CLI client | VMware vSphere, OpenStack, AWS, Azure, Hyper-V, Nutanix, oVirt and others | OpenStack and many other platforms | Yes: Replicas with incremental CBT transfers | Not in its docs: Replica syncs can be scheduled | Not in its docs: Not in its docs |
| virt-v2v (opens in a new tab)libguestfs2.12.0 stable, July 2026 | GPL 2.0 or later | CLI, one guest per run | VMware (vCenter, ESXi, VMX, OVA), Xen, Hyper-V | OpenStack (Cinder volumes), oVirt, libvirt, local disks | No: Converts a stopped guest | No: A building block: the tools above add the orchestration | Not in its docs: Leaves the source guest unchanged |
Read from each project's own repository and documentation on 20 October 2026. “Not in its docs” means the documentation doesn't describe it, not that the tool can't do it. Product names belong to their owners and only name the tools. Something changed? Open an issue (opens in a new tab) and the table follows.
Which one fits
Each tool is built for a different road out of vSphere. In each project's own terms, this is where it is the natural choice:
One VM at a time, from a terminal
MigrateKit
A free CLI in a Docker container: sync cycles with Changed Block Tracking while the VM runs, then a cutover command that builds the OpenStack server on the copied volumes.
A web UI and an appliance, towards Platform9
vJailbreak
A K3s appliance on the target cloud with a web UI, a live CBT copy and cutover windows; Private Cloud Director or any OpenStack-compliant cloud, and ESXi hosts re-imaged as Private Cloud Director hypervisors.
Ansible and RHOSO already in the shop
Red Hat's VMware migration toolkit
The vmware-migration-kit as Red Hat Certified Content, run from the CLI or Ansible Automation Platform, with CBT seeding and parallel migrations per conversion host.
OpenStack to OpenStack, with each VM shut off
os-migrate
Idempotent Ansible playbooks over the OpenStack APIs that move networks, images, volumes and instances between clouds.
Many source platforms, under a commercial licence
Coriolis
An appliance with a web UI and a REST API that replicates from VMware, public clouds and others into OpenStack and beyond; migrations need a per-VM licence from Cloudbase.
Hundreds of VMs, and owners who ask when theirs is down
Seamless Migrate
A control plane over os-migrate, the vmware-migration-kit and virt-v2v: a downtime estimate for every VM, waves with a pilot first, approvals, change windows and cutover slots, then verification and a rollback until finalize, for VMware and OpenStack sources alike. GPU VMs and a VM's floating IP and DNS record come along too, as Technology Previews validated in simulation.
Data movers and control planes
Most of these tools are data movers: they copy the disks, convert the guest and create the server on the destination. virt-v2v is the converter underneath MigrateKit, vJailbreak and Red Hat's toolkit. Moving one VM is a copy; moving an estate is a schedule. Someone decides the order, tells each owner when their VM will be down and for how long, approves the cutover and decides whether to go back.
Seamless Migrate is that second layer, and it keeps the data movers: it drives os-migrate for OpenStack sources and the vmware-migration-kit with virt-v2v for VMware, then adds:
- An estimate before anything moves. Every VM gets a downtime estimate for each strategy and the one with the least downtime: 6m warm against 25m 23s cold for a 200 GiB VMware VM. Try yours in the downtime calculator.
- Waves with a pilot first, ordered by risk.
- A cutover only when it may happen: inside the VM's change window, with a second approver and a free cutover slot.
- Verification and rollback. The server must be ACTIVE with its ports and probes up; a failed check deletes the destination server and starts the source VM again, until you finalize.
- One place to watch it: a dashboard with each migration's downtime clock, a REST API with server-sent events, a CLI and Prometheus metrics.
Questions to ask any migration tool
Whichever you evaluate, these answers decide how the migration goes:
- Where can the VMs go? Some tools are built around one vendor's cloud; check that your destination, its release and its deployment tool are in scope.
- Does the VM keep running while its disks copy? Warm copies need Changed Block Tracking on the VM, and some tools a minimum virtual hardware version.
- Does it need VDDK, and who downloads it under VMware's terms?
- How long will each VM be down, and can you tell its owner before the cutover rather than after?
- Who approves a cutover, and when may it happen? Change windows and a second pair of eyes matter more at VM 300 than at VM 3.
- What happens when a VM doesn't boot on the destination? A rollback you have tried beats a runbook you haven't.
- What does production use need: a licence, a subscription, a support contract? Read the license file, not only the product page.
- Is it released and maintained? Look for tagged releases, release notes and recent commits.
For how Seamless Migrate answers each of them on VMware, see the VMware to OpenStack guide.
Commercial and partner tools
Beyond the projects above, commercial tools cover the same road. Hystax Acura, proprietary and licensed by key, replicates live from VMware, public clouds and other platforms into OpenStack distributions and public clouds, and Red Hat lists it as a certified partner tool for RHOSO. Trilio's VMware to OpenStack migration, proprietary as well, targets Red Hat OpenStack Platform with cold and warm modes through its UI, API or CLI.
The OpenInfra Foundation keeps its own list on its VMware migration page, with more vendors among them CONTRABASS Legato, FishOS MoveIt, Mirantis Migration Service and ZConverter Cloud.
FAQ
Choosing a migration tool, answered.
What teams ask while they compare.
What is the best open source tool to migrate VMware to OpenStack?
It depends on where the VMs go and how many there are. For one VM at a time from a terminal, MigrateKit (Apache 2.0) copies warm with Changed Block Tracking. For an appliance with a web UI, aimed at Platform9 Private Cloud Director or another OpenStack cloud, vJailbreak, source-available under the Business Source License. For Ansible-driven moves into RHOSO, Red Hat's VMware migration toolkit, the os-migrate vmware-migration-kit. For hundreds of VMs that need waves, a downtime estimate for every VM, approvals and a rollback, Seamless Migrate (Apache 2.0) drives the vmware-migration-kit and adds that control plane.
Is vJailbreak open source?
Its source is public under the Business Source License 1.1, which Platform9 grants for production use except offering vJailbreak to third parties as a hosted or embedded service that competes with Platform9's paid versions; each version converts to the Mozilla Public License 2.0 four years after its publication. Platform9 calls it open source and free; the Business Source License is not an OSI-approved open source license, so strictly it is source-available.
Which VMware migration tools need VDDK?
MigrateKit requires VMware's Virtual Disk Development Kit (VDDK 8.0.2 in its README). vJailbreak needs it only for its Standard copy method; its default copy method since v0.4.10 does not. Red Hat's toolkit reads disks through nbdkit's VDDK plugin on its default path, and so does Seamless Migrate, which runs that toolkit on a RHEL 9 conversion host with VDDK. Coriolis has its own disk reader with VDDK as an option, and virt-v2v takes VDDK as one input method among several.
Does Seamless Migrate replace os-migrate or virt-v2v?
No, it builds on them. os-migrate moves OpenStack workloads, the vmware-migration-kit copies VMware disks with Changed Block Tracking and virt-v2v converts the guests. Seamless Migrate adds what a migration of a whole estate needs around them: a plan in waves with a pilot first, a downtime estimate for every VM and strategy, approvals, change windows and cutover slots, verification on the destination and a rollback until finalize.
Which tools also migrate OpenStack to OpenStack?
os-migrate, with each instance shut off for its copy; Coriolis and Hystax Acura, under commercial licences; and Seamless Migrate, which moves VMs from RHOSP 17.1 and community OpenStack cold, warm with a snapshot pre-copy, or by storage handover on a shared Ceph cluster or NetApp ONTAP, beside its VMware strategies.
Which tools estimate each VM's downtime before it moves?
Of the tools compared here, Seamless Migrate is the one whose documentation describes an estimate for every VM: its planning model estimates each strategy from the VM's disks, used space and write rate and the link, then picks the one with the least downtime. For a 200 GiB VMware VM it estimates 6m warm against 25m 23s cold. Red Hat publishes benchmark tables for its toolkit.
GET STARTED
Big possibilities.
First, a small pilot.
The demo runs every phase, from pre-copy to cutover, verification and rollback, against simulated clouds on your laptop. No OpenStack needed to try it.
Docker on a Linux server, or Colima on a Mac
$ git clone https://github.com/imransetiadi/seamless-vms-migrationgit clone https://github.com/imransetiadi/seamless-vms-migration$ cd seamless-vms-migrationcd seamless-vms-migration# macOS only: not needed on Linux$ make seamless-colima-upmake seamless-colima-up # macOS only: not needed on Linux$ scripts/compose-init.shscripts/compose-init.sh# simulated clouds, every phase$ make seamless-demomake seamless-demo # simulated clouds, every phaseOpen the local demo (opens in a new tab)Sign in at /login with the admin token compose-init.sh printed. Podman works too: SEAMLESS_ENGINE=podman.