An independent developer is building OpenVDDK, a from-scratch replacement for VMware’s VDDK library, after Broadcom pulled public downloads of that component in late August 2026. VDDK is the piece almost every tool relies on to move virtual machines off vSphere. The project is in private beta, will be free, and its author publishes in-house tests in which it reads disks faster than the original library, although there are no independent measurements yet.
OpenVDDK in 30 seconds
- Broadcom removed public VDDK downloads on 25 August 2026 without notice, leaving new migrations without an official source for the library.
- OpenVDDK is a drop-in replacement for libvixDiskLib: swap the file and restart, with no changes to the application.
- The beta supports HotAdd, NBD and NBDSSL on vSphere 6.7, 7.0 and 8.0, read-only.
- In the project’s own tests, a 200 GiB cold migration took half the time it did with VDDK 8.0.3.
- Public download will come with the first release candidate.
VDDK (Virtual Disk Development Kit) is the VMware kit that lets third-party software read virtual machine disks directly from vCenter and ESXi. Backup tools depend on it, and so do most migration tools: virt-v2v and nbdkit in the KVM world, Red Hat OpenShift’s Migration Toolkit for Virtualization (MTV), Nutanix Move and Azure Migrate, among others. Each of them asked customers to download the library from VMware, because its license does not allow redistribution.
What changed when VDDK disappeared
According to Platform9 and Virtualization Howto, the VDDK download pages started returning errors on 25 August 2026. Broadcom published no announcement and offered no replacement. The only statements are replies from its customer care team, which told customers that the library is no longer available for use or download and that Broadcom keeps its APIs and SDKs for authorized technology alliance partners.
The impact was immediate for VMware exit projects. Red Hat published a support article for MTV customers who could not download the VDDK image and pointed them to Broadcom, since it cannot ship the library itself. Microsoft added a warning about possible restricted access to its Azure Migrate guidance, and Nutanix Move users reported failed downloads of versions 7.0.3.1 and 8.0.3.2. Anyone with a cached copy can keep using it; anyone starting a migration now has nowhere to get it. Tools that do not depend on VDDK, such as the import wizard built into Proxmox VE, are unaffected.
The move comes in the middle of a wave of migrations after VMware’s licensing changes, a topic System Administration has covered in its VMware to Proxmox migration guide. Broadcom has not explained the reason for the withdrawal, and the industry has read it as one more hurdle for customers who want to leave the platform.
How OpenVDDK works
OpenVDDK is a reimplementation of libvixDiskLib.so.8.0.3, the file that migration tools load. Its author, who also created the free VMware-to-KVM migration tool V2K Migrate, says it was written from scratch using public documentation and black-box testing, contains no VMware code and is not affiliated with Broadcom. The goal is that the application does not notice the switch: replace the library file and restart the service.
The beta supports the three usual transports. HotAdd attaches the snapshot disk to a proxy VM, reads it and detaches it; NBD and NBDSSL read directly from ESXi hosts, the latter encrypted. The project stresses that when NBDSSL alone is requested it never falls back to clear-text NBD, and says that in one of its tests three of the four connections opened by VMware’s library did exactly that. SAN transport is not implemented and is out of scope.
- Compatibility: vSphere 6.7 Update 3, 7.0.3 and 8.0.3; vSphere 6.5 is not supported for now.
- Platform: Linux x86-64 with glibc 2.28 or newer, tested on Enterprise Linux 8 and 9.
- Scenarios: cold and warm migrations, CBT (Changed Block Tracking) incremental passes, snapshot chains and virtual-mode RDMs.
- Tested tools: V2K Migrate, virt-v2v 2.7.1, nbdkit 1.38.5 and Migratekit for VMware-to-OpenStack moves.
- Limitations: read-only with no restores planned, and encrypted VMs have not been tested yet.
Every evaluation build ships with an SPDX software bill of materials (SBOM), and the library sends no telemetry: it only connects to the vCenter and ESXi hosts it is pointed at.
Faster in its own tests, with caveats
The numbers the project publishes are striking. In a HotAdd cold migration of a 200 GiB Windows Server 2019 VM from NetApp NFS, OpenVDDK copied at 537 MiB/s against 282 MiB/s for VDDK 8.0.3, and the full migration took 7 minutes 24 seconds against 15 minutes 2 seconds. Opening a 40 GB disk took 1 second against 19,1, and NBDSSL reads ran at 188 MiB/s against 132 MiB/s. According to the project, the output was identical in both cases, checked with SHA-256 hashes and qemu-img compare.
The site itself warns that these are its own measurements, many of them single runs, and that results depend on the environment. The speed comes from keeping several 2 MiB requests in flight, which raises per-request latency at ESXi (18,8 ms against 2,5 ms) and doubles worker CPU usage. It also lists cases where VMware wins: NBDSSL on CPUs without AES instructions, where OpenVDDK reads at 102-104 MiB/s against 158-176 MiB/s, and an iSCSI path capped at about 1 GB/s, where the original library was around 3 % faster.
Cloudnews.tech has already explained how OpenVDDK aims to speed up VMware-to-KVM migrations. For now the project only hands evaluation builds to test partners, and a public download will follow with the first release candidate. Its author says the code will be published under an open-source license, not yet named, and that work is under way to place it under a neutral foundation. For administrators that is good news: a component that depended on a single vendor’s goodwill is starting to have an alternative. Even so, it is worth testing it in non-critical environments before trusting it with a production migration.
Frequently asked questions
What is VDDK and why does it matter?
It is the VMware kit that lets other tools read virtual machine disks from vCenter and ESXi. virt-v2v, Red Hat MTV, Nutanix Move and Azure Migrate use it to migrate away from VMware.
When did Broadcom pull VDDK downloads?
The download pages stopped working on 25 August 2026, with no official announcement. Broadcom told customers the library is no longer available and that it keeps its SDKs for authorized partners.
Can OpenVDDK be downloaded yet?
No. It is in private beta for test partners, and a public download will come with the first release candidate. It will be free, and its author plans to release it under an open-source license.
Is OpenVDDK faster than VDDK?
In the project’s own tests, yes: for example, a 200 GiB migration in half the time. There are no independent benchmarks, and in some cases, such as NBDSSL without AES, VMware’s library was faster.
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