Broadcom's VMware buy got you worried? Give these 5 FOSS hypervisors a spin

These suggestions are like our principles. If you don't like 'em ... we have others

Comment Last month we shared four VMware ESXi alternatives for enterprises hedging their bets over Broadcom's impending takeover of the virtualization giant.

You can find those suggestions and all your comments right here.

But for small to midsized businesses looking for an escape from VMware's stranglehold on virtualization, you may find your next hypervisor is of the free and open source (FOSS) variety. Lord knows you gave us enough recommendations.

While ESXi has long been the obvious choice for virtualization in large enterprise datacenters, VMware's dominance in the virtualization market means companies of all sizes have all-but standardized on the platform – regardless of whether they're running a single server in their network closet, a few racks in a colo, or a full-fat datacenter.

Given the uncertainty as to how Broadcom's now uncontested takeover of VMware will play out, it might be time to consider your alternatives – just in case. The good news is, when it comes to FOSS hypervisors, users are spoiled for choice. Many offer surprisingly good feature parity and enterprise support contracts to boot.

Obviously, this isn't an exhaustive list, and not all of these can or will replace ESXi for everyone. Let us know via email or the comments if there any others you'd like to recommend, and we'll share those, too.

1. Proxmox Virtualization Environment

Admired by home lab builders and SMBs alike, Proxmox is based on Debian Linux and offers support for both the kernel virtual machine (KVM) framework as well as the Linux Container (LXC) runtime.

The type-1 hypervisor supports most x86 hardware from either AMD or Intel and provides a single dashboard for managing hosts, clusters, VMs and containers.

The platform has evolved steadily since its introduction in 2008 to include support for a bevy of enterprise features, including high-availability clusters and live VM migration between hosts. Proxmox also supports storage systems like local volume management, ZFS, and Ceph.

Proxmox will also run on just about any system with at least 1GB of RAM. However, users coming from VMware's ESXi may run into platform limitations on hosts equipped with more than 12TB of memory or more than 768 CPU threads. If you fall into this category, drop me a line – I have questions. And while there isn't a hard cap on the number of hosts per cluster, many recommend against clusters larger than 32.

Proxmox VE is available at no cost under a standard GNU license, regardless of whether it's deployed for personal or enterprise use. For organizations that want or require a support package, Proxmox Server Solutions – the company behind the the FOSS hypervisor – offers paid licenses on a per-socket basis that unlock access to the enterprise software updates and premium support.

2. XCP-ng and Xen Orchestra

For fans of the Xen virtualization stack, XCP-ng is another popular open-source hypervisor.

While a relatively new entrant into the hypervisor arena, XCP-ng's roots actually stretch back to formation of the XCP project in 2010, which sought to provide an open source version of Citrix's XenServer.

XCP-ng was launched in 2018, after Citrix stopped providing XenServer under a free and open source license and rebranded to Citrix Hypervisor.

It is compatible with most x86 systems using AMD or Intel CPUs and at least 2GB of memory. However, the platform is reportedly limited to 5TB of memory and 288 logical cores supported on each host.

Much like ESXi and vSphere, XCP-ng is only part of the what's needed to run a datacenter and is responsible for virtualization on each of the hosts. The actual management console is provided by running something like Xen Orchestra in a VM. This approach enables users to manage large numbers of hosts from a single interface.

It should be noted that XCP-ng, unlike Proxmox, doesn't support containerized workloads natively.

Paid support options are also available for XCP-ng starting at $600 per-host.

3. OpenNebula

Another reader favorite is OpenNebula which provides a cloud-like web interface for managing virtualized and container workloads.

OpenNebula differs somewhat from other hypervisors on this list, because the platform is actually a management plane. You can think of it sort of like a vendor-agnostic take on VMware's vSphere. This means that unlike Proxmox or other hypervisors on this this list, you can't just start spinning up new VMs right out of the gate. Users first need to configure their virtualization hosts. Thankfully, this is a relatively painless process, especially for KVM virtualization.

The platform isn't limited to KVM either, and supports VMware vSphere, LXC/LXD containers, or Firecracker microVMs. Additional virtualization, bare metal, or container services – including Equinix Baremetal, AWS EC2, or Kubernetes clusters – can also be added via optional plug-ins.

Beyond virtualization, OpenNebula also supports a variety of storage frameworks including Ceph and LVM.

OpenNebula Community Edition is available at no cost under the Apache 2.0 license. As with other virtualization stacks on this list, paid support options are available including several through managed service providers.

4. SUSE Harvester

A relative newcomer to the virtualization game, SUSE is best known for its enterprise Linux operating system. However, the company recently launched its open source Harvester hyperconverged infrastructure platform.

SUSE bills Harvester as a means to manage and consolidate virtual machine workloads alongside Kubernetes clusters from a single unified dashboard. When paired with Rancher, the platform can even automate the deployment of VMs for new Kubernetes clusters.

Harvester is based on Linux and uses the Kubernetes Kubevirt virtualization stack as opposed to KVM or Xen, and the storage system is built on top of the Longhorn block-storage framework.

Compared to Proxmox or XCP-ng, Harvester is not a lightweight hypervisor. The minimum specifications call for an eight-core processor, 32GB of memory, and 140GB of SSD or NVMe storage. What's more, Harvester is specifically designed to be deployed in a clustered environment – meaning you'll want to have at least three machines to get started.

Because Harvester is still relatively new — the 1.0 release only hit late last year — some users may find features lacking or outright missing from the web GUI.

Harvester is offered at no cost under an Apache 2.0 license. For users that want or need additional support, SUSE does offer a subscription support service, but doesn't publicly disclose pricing.

5. Oracle VM VirtualBox

It's hard to talk about free and open source virtualization without at least mentioning Oracle — previously Sun — VirtualBox.

For many, including myself, the cross-platform hypervisor was our first introduction to desktop virtualization, and it remains a viable alternative to closed-source desktop hypervisors like VMware Workstation and Fusion, Parallels, or Microsoft's Hyper-V.

VirtualBox runs on just about any host operating system you can imagine, including Windows, Linux, Mac, and Solaris hosts, and supports an even broader range of guest operating systems.

The base package is available under GNU version 2 license. However not all functionality is open source – many features, like USB 2.0 and 3.0 support, require a separate plug-in available under a personal use and evaluation license from Oracle.

Customers who wish to deploy the VirtualBox expansion pack in a commercial environment can purchase an enterprise license from Oracle for $50 per user. But it should be noted that Oracle requires a minimum order of 100.

A word on support

Regardless of which hypervisor you opt for, getting a support contract from any of the aforementioned vendors may not be the end of the story.

Customers should take steps to validate that their chosen platform actually meets their needs – whether that's support for a specific storage framework, cluster size, or some other obscure detail critical to your business operations.

Thankfully, because these these are all free and open source, it's not all that difficult to spin up a proof concept on spare server, or even in your existing virtualization stack — just don't forget to enable nested virtualization in the VM settings.

You should also ensure your IT staff or MSP partners are prepared to support your chosen platform. Many vendors offer training in addition to support contracts.

Finally, software compatibility isn't guaranteed. And even if you can get your workloads running on a competing hypervisor, FOSS or otherwise, that doesn't mean the software vendor will support that use case.

For example, if a customer has deployed SAP HANA on ESXi and they want to make the switch to another hypervisor, they may find that SAP is unwilling to provide support when its software is running on an unvalidated platform.

While FOSS hypervisors won't replace ESXi for everyone, those willing to take a chance may be surprised to discover just how few compromises they have to make. ®

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