QEMU vs. KVM: Discover the Leaders in Virtualization


QEMU vs. KVM: Discover the Leaders in Virtualization.


What is Virtualization?

Virtualization is a technology that allows the creation of a virtual version of a physical resource such as a server, storage device, network, or operating system. Here are some key points:

  1. Resource Abstraction: Virtualization abstracts physical hardware resources, enabling multiple virtual instances to run on a single physical system.
  2. Types: It encompasses various types, including server virtualization, storage virtualization, network virtualization, and desktop virtualization.
  3. Hypervisors: Hypervisors, either Type 1 (bare-metal) or Type 2 (hosted), are software layers that create and manage virtual machines (VMs).
  4. Resource Efficiency: By consolidating workloads on fewer physical devices, virtualization maximizes resource utilization and reduces hardware costs.
  5. Isolation: Each virtual machine operates independently, ensuring isolation and security between VMs on the same host.
  6. Scalability: Virtualization facilitates easy scalability, allowing quick deployment and management of additional virtual resources as needed.
  7. Disaster Recovery: Virtual machines can be easily backed up, cloned, and migrated, enhancing disaster recovery and business continuity strategies.
  8. Legacy System Support: It allows legacy applications to run on newer hardware, extending the life of outdated software.
  9. Development and Testing: Virtualization enables developers to create isolated environments for testing and development without interfering with production systems.
  10. Cloud Computing: It is a foundational technology for cloud computing, enabling the dynamic allocation of resources in public, private, or hybrid cloud environments.


Prior to delving into the concepts of “KVM” and “QEMU”, it is imperative to first understand the essence of a hypervisor. A hypervisor serves as a sophisticated mechanism that establishes a distinct boundary between the hardware components of the host and the operating system of a computer. There exist two categories of hypervisors, namely type-1 and type-2, each operating in a unique manner. The type-1 hypervisor, often referred to as a bare-metal hypervisor, assumes the responsibility of executing instructions on the host’s hardware. On the other hand, the type-2 hypervisor, recognized as a hosted hypervisor, generates virtual environments across various devices while functioning within a traditional operating system.


  • QEMU, short for Quick Emulator, is open-source virtualization software that emulates CPUs and hardware.
  • You can use QEMU to run operating systems and applications incompatible with your host operating system hardware platform.
  • Essentially, QEMU is a hardware virtualization tool that enhances virtual machine performance.
  • For example, QEMU can help you run ARM software on an x86-based Linux computer, despite the incompatibility with your x86 hardware.
  • By emulating a full system, QEMU allows you to run different operating systems without rebooting your computer.
  • To compare QEMU and KVM briefly: QEMU runs on both Windows and Linux, while KVM operates only on Linux-based host OS.


  • KVM stands for Kernel-based Virtual Machine, which turns your Linux system into a type-1 (bare-metal) hypervisor.
  • KVM allows you to create isolated virtual environments.
  • Built into the Linux operating system code, KVM includes all the features of the Linux kernel.
  • To get the best KVM experience, implement it on a supported Linux distribution, such as Ubuntu or CentOS.


When it comes to KVM vs QEMU, you need to know that KVM acts as an outer guard that monitors QEMU executions to make sure the performance level is at its highest. But how does KVM enhance performance, you may ask? Imagine you partition the CPU to make a virtual CPU for your virtual environment. By providing hardware-assisted virtualization, KVM allows mapping between the vCPU and the actual CPU. This way, all the tasks that are delegated to vCPU get executed on one tiny slice of the physical CPU. KVM runs as a Linux kernel module. That’s how it can offer hardware-assisted virtualization and not sacrifice performance.

  • Operating System Support:
    • QEMU: Supports Linux, Microsoft Windows, macOS, and some other UNIX platforms.
    • KVM: Supports Linux, macOS, and some other UNIX platforms.
  • Open-source and Free:
    • Both QEMU and KVM are open-source and free.
  • Disk Image Formats:
    • QEMU: Supports multiple disk image formats.
    • KVM: Does not support multiple disk image formats.
  • Live Migration:
    • QEMU: Live migration can be done through a complicated process.
    • KVM: Supports live migration natively.
  • Executing Multiple Virtual CPUs in Parallel:
    • QEMU: Supports executing multiple virtual CPUs in parallel.
    • KVM: Supports this depending on the load limits of guest virtual machines.
  • Integration with Different VM Solutions:
    • QEMU: Integrates with various VM solutions like VirtualBox, Xen-HVM, Win4Lin Pro Desktop.
    • KVM: Limited to a maximum of 4 virtualized (emulated) IDE devices per guest virtual machine.
  • Running Docker Instances:
    • QEMU: Generally cannot run Docker instances.
    • KVM: Can run Docker instances.
  • Dynamic Memory Management:
    • QEMU: Does not support dynamic memory management.
    • KVM: Supports dynamic memory management.
  • Virtual Hardware Support:
    • QEMU: Has limited virtual hardware support.
    • KVM: Offers extensive virtual hardware support.
  • Native GUI:
    • Both QEMU and KVM have limited native GUI support.
  • Multipath I/O:
    • Both QEMU and KVM support multipath I/O.
  • Memory Management:
    • QEMU: Utilizes user-mode memory.
    • KVM: Includes memory management features of Linux.
  • Latency:
    • QEMU: Has higher latency compared to KVM.
    • KVM: Offers low latency.
  • Processor Support:
    • Both QEMU and KVM support 32-bit and 64-bit processors.
  • Minimum RAM for Host OS Configuration:
    • Both QEMU and KVM require a minimum of 1 GB RAM for configuring the host OS.
  • SMP (Symmetric Multiprocessing) Hosts:
    • Both QEMU and KVM support SMP hosts.
  • SMP Guests:
    • QEMU: Supports up to 255 CPUs for SMP guests.
    • KVM: Supports up to 16 CPUs for SMP guests.

Advantages of KVM Vs QEMU Virtualization 

With all the hot talk about virtual machines, more and more people are eager to learn about the actual benefits of virtualization software, which could take their business, trading, gaming, etc., to a higher level. So let’s go over some of the KVM vs QEMU advantages.

  • Use of hardware resources on a software level

Since virtual machines use physical resources in most cases, the guest OS can use physical hardware, such as host memory, CPUs, or storage space, freely and more efficiently.

  • Configuration control 

You can configure virtual machines directly from the host, which means you have software-level control over the configuration process.

  • Host OS stability and security

Virtualized kernels are separate from the host operating system. Since a guest operating system runs on virtualized kernels, your host OS’s stability and security are protected should your guest OS encounter failures.

  • Budget-friendly 

Physical servers cost a fortune, and you cannot risk your entire budget only to learn you could have invested in a far superior option; virtualization software. The best thing about VM is that it cuts all the maintenance costs that will inevitably accompany even the best physical server.

  • Free and open-source

Using open-source software can be a huge plus for optimizing telecommunication systems, inventory, accounting, personal productivity applications, contact management, and operating systems. Open-source software offers reduced hardware costs, integrated management, license management, scalability, and many other benefits.

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