Bare Metals vs Virtual Machines vs Containers

 

A bare metal server is a physical computer that is single tenant only. Bare metals gives us a complete control over the hardware resources and the software stack to run. For software applications thats require absolute high performance from hardware, a bare metal could be a good way to go. Bare metal servers are physically isolated. The isolation provides two benefits. first, it is not affected by the noisy neighbour problem. This problem occurs when one tenant performance is impacted because of the activities of another tenant sharing the same hardware. second, the isolation provides the highest level of security. For eg it is not affected by side channel attacks. These attacks takes the advantage of the design flaws in modern microprocessors to allow malicious tenant to allow secrets from its neighbours. This strong security guarantee is another reason to user bare metal. When the application needs to meet the most stringent security, compliance or regulatory requirements, baremetal could sometime be the only way to go. Downside of baremental is, it is expensive, hard to manage, and hard to scale. Acquiring new hardware takes time and it takes a competent team to manage them well.

A virtual machine is an emulation of the physical computer. This is called virtualization. Many virtual machines can run on a single piece of bare metal hardware. On top of the bare metal hardware, is the host OS. Running on top of the host OS is the special piece of software called a hypervisor. This is also known as the virtual machine monitor. The hypervisor manages virtual machines, It creates an abstraction layer over the hardware, so that multiple OS can run alongside each other. Each virtual machine has its own Guest OS. On top of each guest OS runs the applications for the tenant. There is concept called baremetal hypervisor, not to be confused with bare metal hardware. 

A baremetal hypervisor controls the hardware directly without relying on Host OS. This gives the hypervisor full control over the hardware and provides higher performance. However, the hardware that supports the bare metal hypervisor is more expensive. 

We can choose virtual machines pretty much any size to fit our workloads, from general purpose ones with just a few cpu cores and few GB of memory to the high performance ones with hundred of cores and terabytes of memory. 

Benefits of Virtual machines.

Virtual Machines are cheaper to runs. Many of them share the same hardware allowing much higher resource utilization. They are easier to scale too. This provides an organization more flexibility too. Scaling up virtual machines is much easier both horizontal and vertical scale. We can also move one virtual machines from one bare metal hardware to another without shutting down the VM. 

Downside to VM

Virtual Machines could be vulnerable to the noisy neighbor problem described earlier. If our application co-locates with a resource hog of a neighbor, our own application could suffer. Also, virtual machines running on the same  BM hardware share the same physical cpu cores. They are vulnerable to attacks that aim at design flaws in modern processors. Side channel attacks like Meltdown and Spectre are some well known examples. 

Containers

A container is lightweight and standalone package of an application with all its dependencies like libraries, framework and runtime. Containerization is considered to be a lightweight version of virtualization. Like virtualization, here we have a bare metal hardware and a host operating system but instead of virtualizing the hardware with hypervisor, we virtualize the OS itself, with a piece of special software called the container engine. On top of container engines runs many containers. Each of these is its own application environment isolated from each other. The container engines provides even faster resource provisioning. And all the resources need to run the application are packaged together, so that application can run anywhere. Containers are scalable and portable. They are lightweight and requires less hardware resources to run than virtual machines. A bare metal server can host significantly more containers then virtual machines. Since each container runs, as a native process of the host OS, they are much faster to start too. All these makes container even easier to deploy and maintain at scale. However containers are potentially less secure. They share the same underlying OS and the isolation relies on the OS-level primitives.  This means containers are exposed to wider class of vulnerabilities at the OS level.

It is possible to run containers inside the virtual machines. Why we want to do that? One reason is that it provides better security by reducing the possible attack surfaces. This is a trade off between security and flexibility. 

What comes after containers?

Serverless and edge computing comes to mind. They make a developer productivity and deployment stories more compelling but with their own set of tradeoffs. 

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Bare metal servers, virtual machines (VMs), and containers are three different approaches to deploying and managing applications and workloads in IT environments. Here's an overview of each approach along with their characteristics and use cases:

1. **Bare Metal Servers**:

   - **Definition**: Bare metal servers, also known as physical servers or dedicated servers, are physical hardware servers that are directly installed and run an operating system (OS) and applications without any abstraction layer.

   - **Characteristics**:

     - Bare metal servers provide direct access to physical hardware resources, including CPU, memory, storage, and networking.

     - Each bare metal server runs its own instance of the operating system, allowing for full isolation between different workloads.

     - Bare metal servers typically offer high performance and low latency, making them suitable for applications with demanding performance requirements.

     - Managing bare metal servers involves physical provisioning, configuration, and maintenance, which can be more time-consuming and complex compared to virtualized or containerized environments.  

   - **Use Cases**:

     - High Performance Computing (HPC): Bare metal servers are commonly used for HPC workloads, scientific computing, and data analytics applications that require maximum computational power and minimal overhead.

     - Legacy Applications: Legacy applications that are not designed to run in virtualized or containerized environments may require deployment on bare metal servers for compatibility and performance reasons.

     - Regulatory Compliance: Some industries, such as finance, healthcare, and government, have strict regulatory requirements that mandate physical isolation and control over hardware resources, making bare metal servers a preferred choice.

2. **Virtual Machines (VMs)**:

   - **Definition**: Virtual machines are software-based representations of physical computers that run on top of a hypervisor, which abstracts and virtualizes physical hardware resources.

   - **Characteristics**:

     - VMs provide a layer of abstraction between the underlying physical hardware and the guest operating systems and applications running on them.

     - Each VM is encapsulated within its own virtualized environment, including virtual CPU, memory, storage, and network interfaces.

     - Virtualization allows multiple VMs to run concurrently on a single physical server, enabling better resource utilization and consolidation.

     - VMs offer flexibility, scalability, and isolation, making them suitable for a wide range of applications and workloads.  

   - **Use Cases**:

     - Server Consolidation: VMs are commonly used for server consolidation, where multiple virtual machines are deployed on a single physical server to reduce hardware costs and improve resource utilization.

     - Development and Testing: VMs provide isolated development and testing environments that can be easily created, cloned, and disposed of as needed, making them ideal for software development and testing.

     - Legacy Application Migration: VMs can be used to migrate legacy applications from physical servers to virtualized environments without requiring modifications to the application code or architecture.

3. **Containers**:

   - **Definition**: Containers are lightweight, portable, and self-contained units of software that package application code, runtime, libraries, and dependencies, along with configuration files, into a single package.

   - **Characteristics**:

     - Containers share the host operating system's kernel and resources, allowing them to be more lightweight and efficient compared to VMs.

     - Each container runs as a separate process isolated from other containers, providing process-level isolation while sharing the underlying OS kernel.

     - Containers can be rapidly deployed, scaled, and orchestrated using container orchestration platforms like Kubernetes or Docker Swarm.

     - Container images are immutable and declarative, enabling consistent deployment across different environments and infrastructure platforms.  

   - **Use Cases**:

     - Microservices Architecture: Containers are well-suited for building and deploying microservices-based applications, where different components of the application are packaged as containers and deployed independently.

     - Continuous Integration/Continuous Deployment (CI/CD): Containers facilitate the automation of software development processes by providing consistent environments for building, testing, and deploying applications.

     - Cloud-Native Applications: Containers are a key technology for building cloud-native applications that are designed to run in distributed, dynamic, and scalable environments like public and private clouds.

In summary, bare metal servers provide direct access to physical hardware resources, virtual machines offer flexibility and isolation through virtualization, and containers provide lightweight and portable encapsulation of applications and dependencies. Each approach has its own advantages, use cases, and trade-offs, and the choice between them depends on factors such as performance requirements, resource utilization, scalability, and operational considerations.