What is Citrix Hypervisor and what alternatives are there?

Citrix Hypervisor is known for its stability and high performance. However, in some situations, an alternative may be the better option. We’ll take a look at when you should go with a different virtualisation solution.

What is Citrix Hypervisor?

Citrix Hypervisor is a virtualisation platform from Citrix Systems. The hypervisor began as the open-source project Xen, which was started by the University of Cambridge in 2003. Citrix Hypervisor is a bare-metal virtualisation solution, which means it’s directly installed on the physical hardware of a server. The hypervisor is used to run numerous virtual machines (VMs) on a single server. By managing hardware resources like CPU, memory and disk space, it ensures an optimal distribution of resources on different virtual machines.

Citrix Hypervisor supports a range of operating systems including Windows and various Linux distributions. With Citrix, you can automatically create backups and migrate VMs live. Management tools like XenCenter are also available and can be used to monitor and manage VMs and resources.

What are the best alternatives to Citrix Hypervisor?

Some virtualisation solutions offer specific features or technologies that are better suited for certain use cases. Below, we’ll take a look at three alternatives to Citrix Hypervisor that may be better suited to what you need.

KVM

Similar to a type 1 hypervisor, KVM (Kernel-based Virtual Machine) operates directly on the hardware level by using the virtualisation capabilities of modern processors (such as Intel VT or AMD-V). However, KVM needs a host operating system (typically Linux) to run on, and in that respect, it’s more similar to a Type 2 hypervisor. This is why the Xen alternative can be thought of as a hybrid hypervisor.

KVM supports various virtual disk formats, including QCOW2 and RAW. It also allows direct passthrough of physical drives to VMs. KVM is often used with management tools like libvirt to simplify VM management. You can use the API provided by libvirt to control your virtualisation environments.

KVM also uses Linux cgroups (Control Groups) to monitor VM resource usage, enabling precise management of CPU, memory and I/O resources for each VM. You can set Quality of Service (QoS) policies and bandwidth limitations for network and storage resources to ensure critical VMs are given priority.

Since KVM is integrated directly into the Linux kernel, it benefits from the security mechanisms and features present in the kernel, such as SELinux or AppArmor. These security modules provide advanced access controls and protect VMs from potential threats.

How KVM compares to Citrix Hypervisor

Advantages

• Comprehensive virtualisation environment combined with QEMU und libvirt
• Supports a wide range of guest systems

Disadvantages

• No built-in high-availability features
• Less extensive support

Microsoft Hyper-V

As a Type 1 hypervisor, Hyper-V runs directly on the host’s hardware, making it highly efficient in resource allocation. Hyper-V is compatible with many guest operating systems, including Windows (from Windows XP) and various Linux distributions and FreeBSD. The platform offers precise CPU and memory management, including the allocation of dedicated and dynamic resources for VMs. The dynamic memory feature automatically adjusts resources to accommodate the memory needs of VMs.

When it comes to storage options, Hyper-V supports virtual hard disks (VHDs and VHDXs), the direct assignment of physical drives (pass-through disks), and Windows Storage Spaces. With live migration, running VMs can be moved from one physical host to another without downtime. Hyper-V also enables storage migration. This makes it possible to move a VM’s VHDs to another storage device while the VM is running.

A significant advantage of Hyper-V is its ability to replicate VMs to a different location, enhancing resilience and continuity. Additionally, Hyper-V allows for the creation of snapshots and checkpoints. This makes it possible to save the state of a VM at a specific point in time, facilitating quick rollbacks if necessary.

How Hyper-V compares to Citrix Hypervisor

Advantages

• Hyper-V is integrated directly into Windows Server and certain Windows desktop operating systems.
• Microsoft provides users with user-friendly management tools like Hyper-V Manager and System Center Virtual Machine Manager.

Disadvantages

• Hyper-V is limited to Windows-based host operating systems, such as Windows Server and certain versions of Windows 10/11.
• Windows Server licenses are required to use Hyper-V in enterprise environments.
• For live migrations in highly networked environments, Citrix Hypervisor may be the more stable option.

VirtualBox

Oracle’s VirtualBox is a versatile open-source virtualisation solution. As a type 2 hypervisor, it’s suitable for various versions of Windows (from XP to Windows 11), numerous Linux distributions such as Ubuntu, Fedora and CentOS, as well as MacOS and Solaris. The software offers extensive network options including the configuration of virtual networks like NAT, bridged and host-only. These options make communication between VMs and the physical network easier. VirtualBox also supports virtual switches and network interface cards.

With VirtualBox, you can quickly create an identical environment for testing or development purposes by copying an existing VM. It can, for example, be helpful to clone a base VM that includes all the required tools and settings when creating different test environments. Another advantage of VirtualBox is Guest Additions. These special drivers and software extensions optimise the performance and functionality of virtual machines, including better graphics and a smooth integration of the mouse.

How VirtualBox compares to Citrix Hypervisor

Advantages

• VirtualBox runs on different host operating systems such as Windows, macOS and Linux. This allows for more flexibility when choosing the hardware environment.
• VirtualBox caters to both individuals and businesses.
• The intuitive user interface and straightforward installation process are ideal for those new to virtualisation software.

Disadvantages

• In large-scale enterprise environments with a large number of VMs, VirtualBox may not be able to keep up with Citrix when it comes to performance.
• When compared with Citrix Hypervisor, VirtualBox lacks some advanced enterprise features such as advanced network configurations, built-in high availability features and failover mechanisms.
• VirtualBox doesn’t scale as easily as Citrix, making larger environments a challenge to manage.