What is server virtualization?

In computing, a single physical server can be segmented into multiple isolated and individual virtual servers through specialized software. This is called server virtualization, where each virtual server is capable of running its own operating system (OS) and applications completely independent of others on the same hardware.

This technology fundamentally transforms how computing resources are utilized, enabling organizations to extract maximum value from their server hardware investments. It also enables tighter controls over all server users, where they can only access resources assigned to their unique instance, preventing them from affecting other users on the server.

Let’s dive deeper into how server virtualization works and explore the different approaches that can help optimize your IT infrastructure.

How server virtualization works

As mentioned previously, a physical server typically runs a single OS with dedicated applications in traditional computing setups, which often results in significant resource underutilization and high energy consumption.

Server virtualization transforms this model by inserting a software layer – called a hypervisor or virtual machine monitor (VMM) – between the hardware and the operating systems. This layer creates and manages multiple virtual machines (VMs), each functioning as an independent server with its own OS and applications and completing tasks by dividing up the resources across the parent server.

The virtualization process works through these key mechanisms:

1. Resource abstraction: The hypervisor creates a layer that separates physical hardware resources from the virtual environments that use them. This allows multiple operating systems to share the same physical components without conflict.
2. Resource allocation: The hypervisor dynamically allocates CPU power, memory, storage, and network bandwidth to each virtual machine based on configured requirements and usage patterns. Modern hypervisors support features like overcommitment, where more virtual resources can be allocated than physically exist, based on the assumption that not all VMs will need maximum resources simultaneously.
3. Hardware emulation: For each virtual machine, the hypervisor presents virtualized hardware (virtual CPUs, network adapters, storage controllers) that appears to the guest operating system as physical hardware.
4. Isolation: Each virtual machine operates in its own environment, with its own dedicated virtual hardware, operating system, and applications. This isolation prevents problems in one VM from affecting others.
5. Management layer: Advanced virtualization platforms include tools that enable administrators to create, modify, migrate, and monitor virtual machines across the infrastructure.

Types of server virtualization

There are several types of server virtualization that network administrators rely on to solve problems related to resource management, infrastructure costs, and IT demands.

1. Full virtualization

With full virtualization, the hypervisor splits up the server’s resources between completely independent virtual servers. It handles how resources are allocated between each virtual server. Since the virtual machines are separate, they all run on their own operating systems and can be configured as needed.

2. Para-virtualization

Para-virtualization is somewhat related to full virtualization, but with a key difference in how VMs interact with the hypervisor. In para-virtualization, guest operating systems are modified before installation to be aware they’re running in a virtualized environment. These modified guest OSes use specialized interfaces (hypercalls) to communicate directly with the hypervisor instead of relying on complete hardware emulation. Because they can communicate more efficiently with the hypervisor, there are fewer resource demands on the system, meaning more of the physical server’s resources are available for the virtual machines themselves.

3. Hardware-assisted virtualization

With hardware-assisted virtualization, the division of resources needed to support multiple VMs is already built into the CPU of the host server. This allows virtual machines to communicate directly to the main server rather than entirely through the hypervisor. It’s a way to partially cut out the middleman, though a hypervisor is still needed. Since the path between the virtual machines and the physical server is more direct, it reduces the hypervisor’s overhead and resource consumption.

4. OS-level virtualization

With full virtualization, para-virtualization, and hardware-assisted virtualization, a hypervisor is needed to provide a platform on which virtual servers’ operating systems can run. With OS-level virtualization, however, the host server’s OS is set up to allow for multiple isolated instances called containers. Unlike hypervisor-based VMs, containers don’t require separate operating systems and use fewer system resources, which results in much lower computing overhead. This efficiency makes OS-level virtualization lighter and faster, though with less isolation than full virtualization, as well as simpler to implement.

5. Hypervisor-based virtualization

With hypervisor-based virtualization, software (the hypervisor) virtually emulates the hardware of the main server, basically acting like the physical machine on which operating systems can run. The hypervisor allocates the physical server resources across the various guest virtual machines. Full virtualization and para-virtualization are types of hypervisor-based virtualization.

Implementing server virtualization successfully

Successful implementation of server virtualization requires careful planning and adherence to industry best practices.

1. Planning and deployment

• Assessment and inventory: Begin by thoroughly assessing your current infrastructure, cataloging existing servers, applications, dependencies, and performance requirements.
• Hardware selection: Choose hardware with sufficient CPU, memory, storage, and network capacity to handle your virtualized workloads with room for growth.
• Virtualization platform selection: Select a virtualization platform that aligns with your organization’s needs, considering factors like management features, supported guest operating systems, and licensing costs.
• Pilot implementation: Start with non-critical applications to gain experience and validate your virtualization strategy before migrating mission-critical workloads.

2. Resource allocation strategies

• Right-sizing VMs: Allocate resources based on actual needs rather than transferring physical server specifications directly to virtual machines.
• Resource pools: Create resource pools to share CPU and memory efficiently among groups of virtual machines with similar requirements.
• Thin provisioning: Allocate storage space to VMs as needed rather than reserving the maximum anticipated space upfront.
• Memory optimization: Implement memory deduplication and compression technologies to maximize the effective use of physical memory across multiple VMs.

3. Performance optimization tips

• Regular monitoring and tuning: Continuously monitor performance metrics and adjust resource allocations as needed to maintain optimal performance.
• Storage optimization: Use appropriate storage technologies like SSDs for high-performance needs and implement storage tiering to balance performance and cost.
• Network configuration: Configure virtual networks correctly to prevent bottlenecks, considering options like dedicated NICs for high-traffic services.
• VM sprawl management: Implement governance policies to control VM creation and retirement, preventing unnecessary resource consumption.
• Regular maintenance: Keep hypervisors, guest operating systems, and applications updated with security patches and performance improvements.

Pros and cons of server virtualization

Benefits

In addition to streamlining network needs, server virtualization benefits include:

• Saving space: If you’re running one task or application per server, they will soon take over your data center. By hosting multiple virtual servers on fewer physical servers, you can potentially save a lot of physical space.
• Lowering hardware costs: Building physical servers can be costly. Virtual servers are much less expensive to deploy.
• Improving resource efficiency: Many servers are more powerful than needed for the demands they are tasked with, meaning organizations technically pay for unused resources. Virtualization helps ensure that all resources are being used efficiently.
• Lowering energy costs: Since virtualization allows you to use server resources efficiently rather than build unnecessary infrastructure, you have fewer servers using energy.
• Decreasing demand on IT: It shifts the workload from hardware maintenance to more strategic activities. IT teams can manage multiple virtual servers from a single console, automate routine tasks, and reduce time spent on physical hardware troubleshooting.
• Speeding up setup: Days or weeks can go by between purchasing hardware for physical servers and implementation. Setting up virtual servers can take minutes.
• Simplifying disaster recovery: Virtualization offers significant improvements to disaster recovery capabilities through features like snapshots, live migration, and quick replication. Virtual machines can be backed up and restored far more quickly than physical servers, reducing downtime and data loss risks during system failures.
• Improved security: Virtual environments provide enhanced security through logical isolation of workloads. If one virtual machine is compromised, the others and the host system can potentially remain protected, limiting the scope of security breaches.

Challenges

While there are great benefits to server virtualization, it does not come without its share of challenges. Some drawbacks to virtualization include:

• Increasing upfront costs: New hardware and licensing fees can add up to higher upfront costs.
• Performance overhead: The addition of a virtualization layer can introduce overhead and performance issues. While modern hardware-assisted virtualization has reduced this impact, resource-intensive applications may still experience some performance differences compared to running on bare metal, for example.
• Server sprawl: Because VMs are relatively easy to build, administrators can unintentionally create too many of them without proper management or resource planning. This is called “VM sprawl“, which can lead to inefficient resource usage, increased licensing costs, and more complex management.
• New security risks: While overall security is enhanced with VMs, it is important to take into account the new security considerations that arise from virtualization, as hypervisors themselves can become targets for attacks, and proper configuration is essential to maintain isolation benefits.

Server virtualization security

As mentioned before, server virtualization introduces both security benefits and challenges that organizations need to be prepared for before implementation.

Benefits

• Isolation: VMs operate in isolated environments, so even if an attacker compromises one VM, the hypervisor prevents it from affecting others.
• Snapshots and rollbacks: The ability to create snapshots allows for quick recovery from security incidents by rolling back to a known good state without extended downtime.
• Testing security patches: Virtualization creates testing environments where security patches and updates can be tested before deployment to reduce the risk of update-related outages or compatibility issues.
• Improved disaster recovery: Virtual environments can be quickly backed up and restored through techniques like continuous replication and live migration, minimizing downtime after security incidents.

Challenges

• Hypervisor vulnerabilities: The hypervisor represents a critical security boundary, which itself can become a target for attacks if vulnerable. If compromised, it could potentially give attackers access to all hosted VMs.
• VM escape attacks: Sophisticated attacks might allow malicious code to break out of or “escape” from a guest VM containment and access the host or other VMs.
• Resource contention: In multi-tenant environments, security monitoring and controls may consume significant resources, potentially affecting performance.
• Complex security management: With multiple VMs running different OSes and applications, organizations must carefully plan and monitor security across multiple layers (physical hardware, hypervisor, virtual networks, guest operating systems, and applications), each with unique security requirements and potential blind spots.

To address these challenges effectively, here are some best practices for organizations to keep in mind:

• Implement proper network segmentation using virtual firewalls and software-defined networking.
• Maintain regular security patches for both VMs and hypervisors using automated vulnerability scanning and patch management tools.
• Use encryption for VM data storage and protect VM encryption keys from unauthorized access.
• Implement strong access controls and authentication mechanisms.

Common use cases of server virtualization

Server virtualization has become essential across various industries due to its benefits for flexibility and efficiency. Here are some of the most common applications:

1. Data center transformation

Virtualization can be used to transform static data centers into responsive environments that adapt to changing business needs by creating dynamic resource pools that automatically scale based on workload.

2. Development and testing environments

Virtualization provides developers with isolated environments to build and test applications without affecting production systems. These environments can be quickly created, cloned, or reset to various states, accelerating development cycles and improving software quality.

3. Legacy application support

Virtualization allows organizations to run legacy applications on modern hardware by creating virtual environments that mimic older operating systems. This extends the lifespan of critical business applications while benefiting from newer, more reliable hardware.

4. Cloud infrastructure

Virtualization forms the foundation of cloud computing services. Cloud providers use this to create flexible and scalable environments that can be provisioned on demand for their customers.

Server virtualization: What to consider

Virtualized servers can help improve an organization’s computing systems in multiple ways. They allow IT to concentrate less time on the internal network, save space in the data center, maximize server resources, and cut costs associated with hardware and energy. On top of all that, setting up a virtual machine is much simpler than setting up a new physical server.

However, server virtualization is often associated with shared server resources or multi-tenant solutions. While multi-tenant servers are more cost-effective and can be very powerful, they are often associated with possible challenges like noisy neighbors and additional security or stability issues.

One way to mitigate these risks is to choose a bare-metal virtualization approach. With bare metal virtualization, you are the single tenant using the server’s resources, even though there is still a hypervisor managing the virtual servers. Bare metal virtualization can give you all the benefits of cloud computing while minimizing the risks associated with shared server configurations.

Liquid Web knows virtualization

While it’s possible to set up your own hypervisor or OS-level virtualization in your local server room, you don’t have to run your virtual machines on your own private on-premises physical servers. Liquid Web offers a variety of hosting options to fit your needs.

At the entry level, you could select a traditional bare metal server and install your own virtualization software. If you need a simple path to taking advantage of bare metal virtualization, our cloud servers offer single-tenant virtualized servers, giving you the power and performance you need in one package.

If you need the ultimate solution for performance and flexibility, Liquid Web’s VMware Private Cloud will provide you with everything you need. From load balancing to DDOS protection and High Availability Databases, you will have an industry-leading enterprise solution at your fingertips.

Contact us today to learn how to start taking advantage of the power of virtualization for all your server hosting needs.