Virtualization has come quite far today from the time of its invention in the 1960s. It was the time of mainframes and International Business Machines (IBM) pioneered the concept of Virtual Machines and brought it into the commercial realm. IBM’s CP-67 software helped run different applications together, maximizing utilization of the hardware resources.
The concept of virtualizing or partitioning the mainframe was utilized by VMware to launch x86 servers with virtualization in the year 1999.
The technology that played a key role in the future of IT with the advent of cloud, has helped shape the hosting and data center industry to its present state. However, there is still a lot of confusion surrounding it. Hence, the purpose of this article is to discuss the basics like what is server virtualization, what are the benefits of server virtualization and which software is best for virtualization along with an in-depth comparison of different server virtualization software.
What is server virtualization?
Virtualization is the process of creating a virtual (logically isolated) form of an IT environment. There are different types of virtualization – server virtualization, application virtualization, storage virtualization, data virtualization, desktop virtualization and network virtualization to get increased efficiency and cost-effectiveness. Traditionally, servers could run only one application and one operating system, leading to highly inefficient resource utilization.
With the help of virtualization technology, multiple applications and operating systems can be run on a single server, thereby increasing overall efficiency of the system.
What is a virtual machine?
A virtual machine (VM) typically utilizes the host’s physical hardware like CPU, disk IO and network adapters. Hypervisor, the layer between physical and virtual spheres, is the foundational core of every virtual infrastructure. It manages the hardware resources of the host machine and it is its responsibility to distribute them efficiently among different virtual machines (VMs).
There are multiple advantages of virtualization that are helping VMs in gaining traction. It increases IT operational efficiency, agility, scalability, improves resource utilization, and provides considerable cost savings.
It helps enterprises save OPEX and CAPEX, reduce downtime, get business continuity and disaster recovery and provision resources and applications faster.
Comparison of different Server Virtualization software
Microsoft Hyper-V, VMware vSphere, Citrix XenServer, and Red Hat’s KVM, are the major open source hypervisors that have taken the virtualization market by storm. Enterprises often have trouble deciding the best hypervisor that can perfectly complement their business.
An in-depth comparison between major virtualization software based on the key factors and features including licensing costs, virtual machine density, training costs, hardware requirements, performance, etc. will make the things easier for IT decision makers and end users to select the best server virtualization software for them.
Microsoft introduced its hypervisor in 2008, and has continued to release new versions along with the new Windows servers. Hyper -V helps one expand or establish a private cloud environment, promotes effective hardware utilization, improves business continuity and makes development and testing more efficient. We have discussed some features for Windows Server 2016 here.
- Discrete device assignment.
- Nested virtualization.
- Quality of service (QoS) for software-defined networks.
- Supports resizing of virtual hard disks, memory, CPU while the VM is running.
- Live migration & Storage Migration.
- Replication (host to host replica for DR purpose).
- Cloud backup.
- Comprehensive security through Windows Active Directory.
- Storage Quality of Service (QoS).
- Supports containerization.
- Windows PowerShell Direct (new).
For more features, you can follow this link: https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/what-s-new-in-hyper-v-on-windows
VMware vSphere is the set of server virtualization products that includes virtualization, management, and interface layers. It comprises following core components- Infrastructure services, including VMware vCompute, vStorage and vNetwork; application services; vCenter Server – single point control across datacenter services; and clients who can access the datacenter via vSphere Client or via web browser.
Features and components:
- It abstracts memory, processors, storage and other resources into multiple VMs.
- vCenter Server: Centralized management tool to configure, provision and manage virtual IT environments. Provides datacenter services like alarm management, access control to ESXi hosts.
- vSphere Client: Enables remote connection to vCenter Server or ESXi from a Windows PC.
- vSphere SDKs: Provides interfaces for third party solutions to access vSphere.
- VM File System: A cluster file system for VMs.
- Virtual SMP: Enables a single VM to use multiple physical processors at a time.
- vMotion: Enables live migration with transaction integrity.
- Storage vMotion: Enables VM file migration from one place to other without service interruption.
- High Availability: If one server fails, VM is shifted to other server with spare capacity to enable business continuity.
- Distributed Resource Scheduler (DRS): Assigns and balances compute automatically across hardware resources available for VMs.
- Fault Tolerance: Generates copy of primary VM to ensure its continuous availability.
- Distributed Switch (VDS): Spans multiple ESXi hosts and enables considerable reduction of network maintenance activities and increases network capacity.
- Network & Storage I/O Control.
- Hot add CPU and RAM resources.
For more information, you can follow this URL:
XenServer is an open sourced product from Citrix, based on Xen Project Hypervisor. It’s a bare-metal virtualization platform with enterprise-grade features that can easily handle workloads, combined OS, and networking configurations. XenServer delivers application performance for x86 workloads in Intel and AMD environments.
It can cater to XenApp and XenDesktop deployments, and offer customers the enhanced virtualized graphics with NVIDIA and Intel. XenServer services allow multiple computer operating systems to execute on same computer hardware.
- Multi-server management
- Dynamic Memory Control
- Live VM migration & Storage XenMotion
- Site Recovery
- Host Failure Protection
- Active Directory Integration
- Role Based Administration and Control (RBAC)
- Mixed Resource Pools with CPU Masking
- Distributed Virtual Switch Controller
- In Memory read caching
For more information, you can follow this link: https://support.citrix.com/content/dam/supportWS/kA460000000CmyyCAC/XenServer_6.5_Feature_Matrix.pdf
Red Hat KVM (Kernel-based Virtual Machine)
Red Hat’s KVM is a complete virtualization infrastructure solution. Kernel-based Virtual Machine turns Linux kernel into a hypervisor. A part of Red Hat Virtualization suite, it was merged into the Linux kernel mainline in kernel version 2.6.20.
Here is an overview of the features of KVM:
- Overcommit resources.
- Disk I/O throttling.
- Hot plug of virtual resources.
- Low cost virtualization solution.
- Red Hat Enterprise Virtualization programming & API.
- Live Migration & Storage Migration.
- Assign any PCI device to virtual machines.
- Container support.
- Disaster Recovery support.
- Red Hat Satellite integration.
For more details, you can follow this URL: https://www.redhat.com/cms/managed-files/vi-rhv4-feature-guide-inc0421083-201607nb-en.pdf
Hypervisor Comparison: Hyper-V vs vSphere vs XenServer vs KVM
|Feature||Hyper-V 2016||vSphere 6.5||XenServer||KVM|
|RAM/VM||12 TB for generation 2;||6 TB||1.5TB||6 TB|
|1 TB for generation 1|
|CPUs/VM||240 for generation 2;||128||32||240|
|64 for generation 1;|
|VM Disk||64 TB for VHDX format;||62TB||2TB||10TB|
|2040 GB for VHD format|
|VM Live Migration||Yes||Yes||Yes||Yes|
|VM Replication supports||Yes||Yes||Yes||Yes|
|Disk I/O Throttling||Yes||Yes||Yes||Yes|
|Hot plug of virtual resources||Yes||Yes||Yes||Yes|
Leading research firm Gartner had depicted VMware and Microsoft as the leaders in their Magic Quadrant for x86 Server Virtualization in 2016.
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