A virtual machine (VM) is a software application that emulates a physical computer system. VMs allow users to run an operating system and programs within the emulated environment as if using a separate physical device. While related, VMs have some key differences from traditional software applications.
- A virtual machine is software that behaves like an independent physical computer, running its own operating system and programs.
- VMs differ from apps in that apps run on top of an existing operating system, while the VM provides the operating system.
- VMs can virtualize hardware like disks, networks, graphics cards, etc to function like independent machines.
- VMs provide more isolation, customization, flexibility with operating systems, but apps offer more mobility and limited requirements.
- VMs require more resources and are persistent, apps are lightweight and can be easily distributed.
Understanding Virtual Machines vs Apps
Architecture and Behavior Differences
The key architectural difference between a VM and app comes down to what it virtualizes and encapsulates.
A typical software application runs on top of an existing operating system and hardware. It accesses the underlying platform’s resources through the OS via APIs and system calls. Apps are designed for the existing environment provided by a device and its OS.
In contrast, VMs actually virtualize and emulate the underlying platform, including virtualized hardware, an operating system kernel, system libraries, storage, memory, etc. This creates an environment behaving like an independent physical computer system on which you can install an OS and software. The VM runs as an application within the host environment, but internally virtualizes a complete system architecture.
So while an app utilizes the existing environment, a VM simulates one or more virtual environments independent of the underlying physical machine.
Hardware Virtualization: A key capability provided by VMs is hardware virtualization. Various components like the CPU, disk, network, graphics cards, etc can be virtualized at a hardware level to appear as separate hardware to the guest OS.
Custom/Multiple OS: VMs also allow running not just multiple apps, but multiple operating systems – each with their own associated apps and libraries. These guest OSes run independently within each VM.
Apps utilize the existing hardware and OS provided by the host computer or mobile device. VMs virtualize separate hardware and can support custom operating systems.
Persistence and Distribution
VMs also provide more persistence – the VM’s disk images, configuration, installed programs all remain saved in between sessions. Apps are generally more transient and lightweight.
Distribution is also different – a VM configured on one device needs to be recreated on another device to access it. Apps are much more mobile and easily downloadable on any device.
In summary, while VMs emulate an entire computer, apps simply extend the capabilities of an existing OS.
Comparing Virtual Machine Use Cases vs Apps
Isolation – VMs provide strong isolation between host and guest environments for security, failure containment, experimentation with different OSes.
Flexibility – VMs allow emulating customized hardware configurations needed by the guest OS and programs. Flexible with infrastructure needs.
Development/Testing – VMs are useful for developers to test code across different environments and OSes. Perfect sandbox.
Legacy Support – Older operating systems can still be used by virtualizing the necessary hardware to run them.
Consolidation – Server consolidation is a major use case. Multiple VMs can run on a single server utilizing the same physical resources efficiently.
Whereas apps are preferred when:
Mobility – Apps can be easily installed, accessed or downloaded on devices. More user-friendly.
Limited Requirements – Apps don’t need the full environment – just the API and services of the host OS.
Cost – Simple apps reduce software licensing compared to OS licenses needed for VMs. Lower resource needs.
So while VMs provide isolation and flexibility to mimic entire computers, apps emphasize mobility and extending capabilities of existing devices.
Key Differences Summary
|Emulates/provides virtual hardware and OS
|Existing OS via programming interfaces
|Hardware, OS, persistent storage
|Fixed to a device, needs recreation
|Easily distributed, downloaded, installed
|Emulated hardware requires more resources
|Lightweight, utilizes existing resources
While virtual machines share some similarities with application software, they differ in their architecture and approach. VMs encapsulate entire virtual hardware and operating systems while apps simply enhance an existing platform through code.
VMs focus on strong isolation between environments and flexibility in configuration rather than easy distribution across devices. This suits them for security, testing, legacy system support etc. Meanwhile lightweight applications emphasize native mobility, access and limited requirements.
Understanding these architectural differences helps clarify when virtual machines versus applications are suitable for a task. Their complementary capabilities expand the possibilities across both software development and infrastructure management in a cloud-connected world where both remain essential technologies.
- What type of software is a virtual machine?
A virtual machine is a type of software that emulates physical computer hardware and runs a complete operating system. This allows virtualizing a full computer system within application software.
- Do I need a VM to run an app?
No, applications run on top of an existing operating system so they do not require virtual machines. VMs emulate hardware that can then run operating systems and applications.
- Can a VM function like a physical computer?
Yes, a VM can perform most functions of a physical computer system while running independently within a host machine using virtualized hardware allocated to it.
- Do VMs have persistence?
Yes, a VM maintains its disk, installed software, configuration etc even when powered off, allowing it to function like a persistent physical computer.
- Can I run apps meant for different OSes on a VM?
Yes, different guest operating systems can be installed on VMs allowing them to run those OS-specific applications within the virtual environment.
- What is application virtualization?
It refers to making applications accessible across locations and devices without installing them locally. This is different from full virtualization where complete system hardware is emulated.
- Is hardware virtualization required for VMs?
Most virtual machines utilize hardware-assisted virtualization support in modern CPUs for efficient performance emulating hardware like CPU, memory and devices.
- What’s the difference between application and process virtualization?
Process virtualization isolates apps from the operating system similar to containers. Application virtualization abstracts apps from clients without installation.
- What VM software programs are available?
Common virtualization platforms that can create VMs include VMware, Hyper-V, VirtualBox, QEMU and more. These work by emulating virtual system hardware.
- Are Docker containers considered VMs?
No, Docker utilizes operating-system-level virtualization by sharing the host system kernel unlike VMs that emulate hardware to boot another kernel.
- Can multiple VMs run on a host simultaneously?
Yes, hypervisors can efficiently schedule resources between virtual machines running different guest operating systems on the same host system.
- How do VMs utilize hardware resources?
The hypervisor allocates a defined set of host physical resources like CPU, cores, memory, storage and devices to virtualized hardware accessed by each VM.
- Do I need virtualization support on my CPU to run VMs?
Modern x86 CPUs have hardware virtualization instructions like VT-x (Intel) or AMD-V that greatly improve performance for VMs using hardware acceleration.
- Are VMs less secure than physical machines?
VMs themselves are isolated from the host and other VMs. But the security depends on the hypervisor, host machine security and how isolated networking is configured.
- Can a VM improve security for high-risk apps?
Yes, VMs can sandbox risky apps inside an isolated environment protecting other apps and systems from issues arising within the VM.
- Are VMs and cloud computing related?
Yes, popular cloud infrastructure like AWS EC2 runs user instances within virtual machines to efficiently utilize data center hardware while isolating customer environments.
- How do I choose between VMs and containers?
Containers provide operating-system-level virtualization for application isolation while VMs offer full hardware virtualization. Use VMs where full guest OSes are needed.