What Is a Virtual Machine (VM)? 

This setup enables users to run different operating systems on the same hardware, enabling higher resource utilization and flexibility in software deployment. VMs are integral to modern computing environments, offering the ability to abstract hardware resources and provide a scalable and secure method of deploying applications and services. 

By decoupling the software from the underlying hardware, VMs enhance the portability of applications, improve disaster recovery processes, and simplify infrastructure management. VMs are also a core component of modern cloud computing platforms.

What Is a Container? 

A container is a lightweight, stand-alone, executable software package that includes everything needed to run a piece of software, including the code, runtime, system tools, libraries, and settings. Containers are designed to run across different computing environments more consistently and efficiently than traditional software environments. 

Unlike virtual machines that virtualize the entire hardware stack, containers do not contain an entire operating system, running directly on top of the existing operating system kernel. This makes them more lightweight and faster to run compared to virtual machines.

Containers have gained popularity for their efficiency, speed, and the ability to package and run applications in a portable, consistent manner across different environments. They reduce the overhead associated with VMs and allow for a more agile development and deployment process. Containers are particularly well-suited to microservices architectures, where applications are broken down into small, independent components.

In this article:

• VMs vs. Containers: Usage and Adoption Statistics
• Advantages of VMs
• Disadvantages of VMs
• Advantages of Containers
• Disadvantages of Containers
• Containers vs. Virtual Machines: Key Differences
• Verdict: When to Use Containers vs. Virtual Machines in 2024

VMs vs. Containers: Usage and Adoption Statistics

Containers have grown in popularity, overtaking virtual machines for many applications. According to Statista, 96% of organizations are using containers across all environments (including development and production). Gartner estimates that global revenue from container management services doubled to $944 between 2020-2024.

Current trends in VMs indicate a shift towards hybrid and multi-cloud architectures, leveraging both on-premises infrastructure and public cloud services. This approach addresses the need for flexibility, resilience, and optimization of workloads across diverse environments.

According to a report by GMI, the primary markets for virtual machines today are banking and financial services (BFSI), healthcare, telecommunications, government and public sector, manufacturing, retail, and media. The BFSI segment is forecasted to grow with a CAGR of 11.5% between 2024 and 2032. Organizations primarily use VMs for two purposes: system virtual machines and process virtual machines, with system VMs accounting for over 60% of the global market share.

Advantages of VMs 

Here are some of the main advantages of virtual machines.

Strong Isolation and Security

VMs provide strong isolation by running each virtual machine as a separate entity, with its own full instance of an operating system, applications, and libraries. This isolation ensures that activities or issues within one VM do not affect others, enhancing the security posture of the environment.

The hypervisor’s role in managing VMs adds an additional layer of security. It can control access to hardware resources, preventing unauthorized access or resource contention among VMs.

Full Guest OS Provides Improved Control and Compatibility

VMs host a full guest operating system, offering comprehensive control over the computing environment. This capability allows for the deployment of applications and services that rely on specific OS configurations or need to interact closely with underlying system components. The full OS environment ensures compatibility with legacy applications and provides a familiar environment for IT administrators and developers to configure and manage.

The presence of a full guest OS also enables more sophisticated system-level operations that might not be feasible with containers. This includes tasks such as advanced networking configurations, detailed security settings, and complex storage setups, giving administrators the flexibility to tailor the environment to meet precise operational requirements.

Resource Allocation and Management

VMs offer robust resource allocation and management features, allowing administrators to precisely control how physical server resources—such as CPU, memory, and storage—are distributed among virtual machines. This capability is crucial for ensuring that applications have the necessary resources to perform optimally while also maximizing the efficiency of the underlying hardware.

Hypervisors, the software that creates and runs VMs, provide tools and technologies to monitor and manage resource usage in real time, enabling dynamic adjustment to meet changing workload demands.

Disadvantages of VMs 

Here are some of the main drawbacks of virtual machines.

Resource Overhead and Inefficiency

When using VMs, there is resource overhead associated with running multiple full-fledged operating systems on a single physical server. Each VM requires a significant amount of system resources to operate its own OS, in addition to the application workloads it supports. This setup can lead to inefficiency, reducing the overall utilization and performance of the hardware.

This overhead impacts the density of VMs that can be hosted on a server and contributes to higher operational costs. Power, cooling, and hardware expenses can escalate as more physical servers are required to accommodate the resource-intensive nature of VM environments.

Slower Boot Times

VMs generally experience slower boot times than containers because they must load an entire operating system each time they are started. This process can be time-consuming, particularly in environments where rapid scalability or fast deployment of applications is crucial. 

The delay in startup times can hinder development processes and delay responses to sudden increases in demand or the need for quick service recovery in case of failure.

Challenging to Manage at Scale

Managing a large number of VMs can be challenging, especially as the infrastructure scales. Each VM operates as a complete and independent system, requiring individual configuration, management, and maintenance. This complexity increases with the number of VMs, making it difficult to ensure consistency, apply updates, and manage configurations.

Automated management tools and infrastructure as code (IaC) practices can help alleviate some of these challenges, but the inherent complexity of VM environments often requires significant administrative effort and expertise. This can lead to higher operational costs and the potential for configuration errors or inconsistencies.

Advantages of Containers 

Here are some of the main advantages associated with containers.

Lightweight and Efficient Resource Use

Containers are inherently lightweight, as they share the host system’s operating system kernel and isolate the application and its dependencies in user space. This architecture reduces the overhead compared to VMs, allowing for more efficient use of system resources. Containers require less memory and CPU to run, enabling higher density on the same hardware and reducing the total cost of ownership.

The efficiency of resource use in containers also improves application performance. This efficiency is particularly beneficial in cloud environments and for applications designed with a microservices architecture, where resources can be precisely allocated and adjusted according to the needs of individual services.

Faster Startup Times

Containers are known for their startup speed, often launching in seconds, compared to the minutes it may take for a VM to boot up its operating system. This rapid startup capability facilitates agile development practices, such as continuous integration and continuous deployment (CI/CD), by allowing developers to quickly test and deploy changes. 

The speed at which containers can be started and stopped makes them appropriate for environments that require elasticity, such as cloud-native applications that need to scale in response to fluctuating demand.

Ease of Management and Scalability

Containers simplify application deployment, management, and scaling. Tools like Kubernetes automate the deployment, scaling, and operation of containerized applications, making it easier to manage complex applications at scale. This ease of management extends to lifecycle management, including updates, monitoring, and resource allocation.

The scalability of containers is particularly well-suited to microservices architectures. Containers can be dynamically scaled to match demand for individual services without impacting the rest of the application, providing a flexible and efficient approach to application scalability and management.

Disadvantages of Containers

Here are some of the drawbacks of containers.

Weaker Isolation than VMs

While containers offer many advantages, they provide weaker isolation compared to VMs. Containers share the host’s operating system kernel, which can create potential pathways for malicious activities to affect the host or other containers. This shared environment can pose risks, especially in multi-tenant scenarios where containers from different users or applications run on the same host system.

The reduced isolation can also lead to potential resource contention among containers, as they compete for the same OS resources. While container orchestration tools provide mechanisms to manage resource allocation, the inherent sharing model of containers can make it challenging to guarantee performance and isolation at the same level as VMs.

Security Concerns Due to Shared Kernel Space

The shared kernel space of containers raises security concerns, as vulnerabilities in the kernel can potentially be exploited to gain unauthorized access to all containers on the host. This risk is exacerbated in environments where containers from different trust levels are co-located on the same host system. 

Container runtime environments and orchestration tools offer features to mitigate these risks, such as namespace isolation, security policies, and network segmentation. However, the nature of container architecture requires careful security planning and management to protect against kernel-level vulnerabilities and ensure the integrity of the containerized applications.

Limited by Host OS Compatibility

Containers are dependent on the host operating system’s kernel, which can limit their compatibility and portability across different OS platforms. Unlike VMs, which can run virtually any computing system regardless of the host’s OS, containers must be compatible with the host kernel.

This limitation means that a container built for a Linux environment, for example, cannot run natively on a Windows host without additional compatibility layers or emulation. It can impact the choice of development environments, deployment platforms, and migration strategies. 

Containers vs. Virtual Machines: Key Differences 

Let’s summarize the key differences arising from the pros and cons discussed above:

1. Underlying Architecture

VMs emulate entire hardware systems, allowing them to run complete operating systems and applications independently of the host. Each VM includes not only the application and its dependencies but also a full guest OS, which interacts with the hypervisor to manage resources on the physical hardware.

Containers virtualize at the operating system level, sharing the host OS kernel and isolating the application in its own user space. This approach enables containers to be more lightweight and efficient, as they do not require the overhead of a full OS instance. The shared kernel model of containers allows for higher density and faster startup times but offers less isolation compared to the hardware-level virtualization of VMs.

2. Performance

Containers, due to their lightweight nature and shared kernel architecture, typically offer better performance, especially in terms of startup time and resource efficiency. The reduced overhead associated with containers allows for more applications to be run on the same hardware, improving scalability and reducing costs.

VMs, while providing strong isolation and security, incur a higher resource overhead due to the need to run a full guest operating system for each instance. This can lead to slower boot times and less efficient use of system resources, potentially impacting application performance and scalability.

3. Isolation and Security

VMs offer strong isolation by running each VM as an independent unit with its own OS, making them well-suited for applications that require strict security measures, compliance, or isolation from other workloads. The hypervisor provides a robust barrier, mitigating the risk of one VM affecting another or the underlying host.

Containers, while isolated at the process level, share the host’s kernel, which can introduce vulnerabilities and limit isolation compared to VMs. The shared kernel model means that a security issue in the kernel could potentially impact all containers on the host. Container technologies include security features to mitigate these risks, but the inherent architecture of containers presents unique challenges compared to the more isolated environment of VMs.

4. Portability

Containers are highly portable, allowing applications to be packaged with all their dependencies and run consistently across different computing environments. This portability is facilitated by the container’s ability to run atop the host OS kernel, eliminating the need for a guest OS and making containers more lightweight and flexible for deployment across platforms.

VMs, while also portable, require the replication of the guest OS environment to ensure consistency, which can introduce complexity and overhead when moving VMs between different hosts or cloud environments. The need for a full OS within each VM can limit their portability compared to containers, which are inherently more adaptable and easier to migrate.

5. Resource Efficiency and Density

Containers share the host OS kernel and require fewer resources to run, allowing for a greater number of applications to be hosted on the same physical or virtual server. This efficiency translates to cost savings, improved performance, and the ability to scale applications more effectively.

VMs each require a full copy of the operating system, leading to higher resource consumption and reduced density on the host hardware. While VMs provide strong isolation and are suited for a broad range of workloads, their resource demands can make them less efficient, especially in environments where scalability and resource optimization are critical.

Related content: Read our guide to Docker vs virtual machine

Verdict: When to Use Containers vs. Virtual Machines in 2024 

The choice between containers and VMs often depends on the use case and needs of the environment and development project.

Environment Configuration

Containers are suitable for scenarios where portability, efficiency, and rapid scalability are paramount. Their lightweight nature allows for quick deployment and scaling, making them well-suited for microservices architectures, cloud-native applications, and continuous integration/continuous deployment (CI/CD) workflows.

VMs are better suited to situations requiring strong isolation, comprehensive security, or compatibility with legacy systems. The ability to run a full guest OS provides a more controlled and isolated environment, which is beneficial for applications with specific OS requirements or when running multiple disparate environments on the same hardware.

Development Velocity

Containers enable a faster development cycle by allowing developers to package applications with all their dependencies, ensuring consistency across different environments. This approach supports agile development practices, enabling quicker testing, deployment, and iteration.

VMs can be slower to deploy and start than containers, potentially impacting development speed. However, they offer a stable and isolated environment that can be crucial for testing applications in conditions that closely mirror production environments. 

Scalability

Containers are inherently more scalable, allowing for easy and efficient scaling of applications. The lightweight nature of containers and their ability to share the host OS resources make them well-suited for dynamic scaling in response to fluctuating workloads.

VMs can also be scaled, but their higher resource requirements and longer startup times may make them less agile in rapidly changing environments. VMs are often used in scenarios where the scalability needs are predictable and where the benefits of strong isolation and security outweigh the need for rapid scalability.

Holistic Container Security with Aqua

Aqua provides a Cloud Native Application Protection Platform (CNAPP) that secures cloud native, serverless, and container technologies. Aqua offers end-to-end security for containerized applications, and protects you throughout the full lifecycle of your DevOps pipeline: from code and build, across infrastructure, and through to runtime controls, container-level firewalls, audit, and compliance.

Continuous Image Assurance

Aqua scans container images for malware, vulnerabilities, embedded secrets, configuration issues and OSS licensing. You can develop policies that outline, for example, which images can run on your container hosts. Aqua’s vulnerability database, founded on a continuously updated data stream, is aggregated from several sources and consolidated to make sure only the latest data is used, promoting accuracy and limiting false positives and negligible CVEs.

Aqua offers Trivy, an all-in one open source security scanner, which now provides multiple capabilities:

• Scanning IaC templates for security vulnerabilities
• Kubernetes operator that can automatically trigger scans in response to changes to cluster state
• Automated generation of software bills of materials (SBOMs)
• Detection of sensitive data like hard-coded secrets in code and containers
• Docker Desktop integration making it possible to scan container images directly from Docker Dashboard

Aqua DTA

Solutions like Aqua’s Dynamic Threat Analysis allow protection against advanced and evasive security threats, including supply chain attacks. The industry’s first container sandbox solution, Aqua DTA dynamically assesses the risks of container images by running them in an isolated sandbox to monitor runtime behavior before they hit the production environment.

Runtime Security for Containers

Aqua protects containerized applications at runtime, ensuring container immutability and prohibiting changes to running containers, isolating the container from the host via custom machine-learned SECCOMP profiles. It also ensures least privileges for files, executables and OS resources using a machine-learned behavioral profile, and manages network connections with a container firewall.

Drift prevention

To enforce immutability of container workloads, Aqua enables drift prevention at runtime. This capability deterministically prohibits any changes to the image after it is instantiated into a container. By identifying and blocking anomalous behavior in running containers, Aqua helps ensure that your workloads are protected from runtime attacks, zero-day exploits, and internal threats.

Aqua further enhances securing containers as follows:

• Event logging and reporting—granular audit trails of access activity, scan container commands, events, and coverage, container activity, system events, and secrets activity.
• CIS certified benchmark checks—assess node configuration against container runtime and K8s CIS benchmarks with scheduled reporting and testing or Aqua OSS tools.
• Global compliance templates—pre-defined compliance policies meet security standards such as HIPPA, CIS, PCI, and NIST.
• Full user accountability—uses granular user accountability and monitored super-user permissions.
• “Thin OS” host compliance—monitor and scan host for malware, vulnerabilities, login activity, and to identify scan images kept on hosts.
• Compliance enforcement controls—only images and workloads that pass compliance checks can run in your environment.

Container Firewall

Aqua’s container firewall lets you visualize network connections, develop rules based on application services, and map legitimate connections automatically. Only whitelisted connections will be allowed, both within a container cluster, and also between clusters.

Secrets Management

Store your credentials as secrets, don’t leave them in your source code. Aqua securely transfers secrets to containers at runtime, encrypted at rest and in transit, and places them in memory with no persistence on disk, so they are only visible to the relevant container. Integrate Aqua’s solution with your current enterprise vault, including CyberArk, Hashicorp, AWS KMS or Azure Vault. You can revoke, update, and rotate secrets without restarting containers.

Learn more about Aqua Container Security