Introduction to Virtualization
Virtualization is an abstraction layer
that creates separate distinct virtual environments allowing the
operation of different operating systems, desktops and applications
under the same or combined pool of resources. In the past couple of
years, virtualization has gained an incredible rate of adoption as
companies consolidate their existing server and network infrastructure,
in hope to create a more efficient infrastructure that can keep up with
their growing needs while at the same time keep the running and
administration costs as low as possible.
Our readers can visit our dedicated Windows Server 2012 Server section to read more on Windows Hyper-V Virtualization and Windows Server 2012 technical articles.
When we hear the word ‘Virtualization’, most think about ‘server virtualization’ – which of course is the most widely applied scenario, however today the term virtualization also applies to a number of concepts including:
- Server virtualization: - Server virtualization allows multiple operating systems to be installed on top of single physical server.
- Desktop virtualization: - Desktop virtualization allows deployment of multiple instances of virtual desktops to users through the LAN network or Internet. Users can access virtual desktops by using thin clients, laptops, or tablets.
- Network virtualization: - Network virtualization also known as Software Defined Networking (SDN) is a software version of network technologies like switches, routers, and firewalls. The SDN makes intelligent decisions while the physical networking device forwards traffic.
- Application virtualization: - Application virtualization allows an application to be streamed to many desktop users. Hosted application virtualization allows the users to access applications from their local computers that are physically running on a server somewhere else on the network.
This article will be focusing on the Server virtualization platform,
which is currently the most active segment of the virtualization
industry. As noted previously, with server virtualization a physical
machine is divided into many virtual servers – each virtual server
having its own operating system. The core element of server
virtualization is the Hypervisor – a thin layer of
software that sits between the hardware layer and the multiple operating
systems (virtual servers) that run on the physical machine.
The Hypervisor provides
the virtual CPUs, memory and other components and intercepts virtual
servers requests to the hardware. Currently, there are two types of
Hypervisors:
Type 1 Hypervisor –
This is the type of hypervisor used for bare-metal servers. These
hypervisors run directly on the physical server’s hardware and the
operating systems run on top of it. Examples of Type-1 Hypervisors are Microsoft’s Hyper-V, VMware ESX, Citrix XenServer.
Type 2 Hypervisor – This is the type of hypervisor that runs on top of existing operating systems. Examples of Type-2 Hypervisors are VMware Workstation, SWSoft’s Parallels Desktop and others.
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Microsoft Server Virtualization – Hyper-V Basics
Microsoft introduced its server virtualization platform Hyper-V with the release of Windows Server 2008. Hyper-V is a server role that can be installed from Server Manager or PowerShell in Windows Server 2012.
With the release of Windows Server 2012 and Windows Server 2012 R2,
Microsoft has made lot of improvements in their Hyper-V virtualization
platform. Features like live migration, dynamic memory, network
virtualization, remoteFX, Hyper-V Replica, etc. have been added to new Hyper-V 3.0 in Server 2012.
Hyper-V is a type 1 hypervisor
that operates right above the hardware layer. The Windows Server 2012
operating system remains above the hypervisor layer, despite the fact
the Hyper-V role is installed from within the Windows Server operating
system. The physical server where Hypervisor or Hyper-V server role is
installed is called the host machine or virtualization server. Similarly, the virtual machines installed on Hyper-V are called guest machines.
Understanding Traditional vs Modern Server Deployment Models
Let’s take a look at the traditional way
of server configuration. The figure below shows the typical traditional
server deployment scenario where one server per application model is
applied. In this deployment model, each application has its own
dedicated physical server.
Traditional Server Deployment
This traditional model of server
deployment has many disadvantages such as increased setup costs,
management & backup overhead, increased physical space and power
requirements, plus many more. Resource utilization of this type of
server consolidation is usually below 10%. Practically, this means that
we have 5 underutilized servers.
Virtualization comes to dramatically change the above scenario.
Using Microsoft’s Windows Server 2012 along with the Hyper-V role
installed, our traditional server deployment model is transformed into a
single physical server with a generous amount of resources (CPU,
Memory, Storage space, etc) ready to undertake the load of all virtual
servers.
The figure below shows how the traditional model of server deployment is now virtualized with Microsoft’s Hyper-V server:
Hyper-V Server Consolidation
As shown in the figure above, all the
five servers are now virtualized into single physical server. It is
important to note that even though these virtual machines run on top of
the same hardware platform, each virtual server is completely isolated
from other virtual machines.
There are many benefits of this type of
virtualized server consolidation. A few important benefits are reduced
management overhead, faster server deployment, efficient resource
utilization, reduced power consumption and so on.
Network Virtualization with Hyper-V
With the power of network virtualization
you can create multi-tenant environment and assign virtual machines or
group of virtual machines to different organizations or different
departments. In a traditional network, you would simply create different
VLANs on physical switches to isolate them from the rest of the
network(s). Likewise, in Hyper-V, you can also create VLANs and virtual switches to isolate them from the network in the same way.
Readers can also refer to our VLAN section that analyses the concept of VLANs and their characteristics.
For example, you can configure a group
of virtual machines on the 192.168.1.0/24 subnet and other group of
virtual machines on 192.168.2.0/24 subnet.
Hyper-V Networking
Each virtual machine can have more than
one virtual network adapter assigned to it. Like regular physical
network adapters, the virtual network adapters can be configured with IP
addresses, MAC addresses, NIC teaming and so on. These virtual network
adapters are connected to a virtual switch. A Virtual switch is
a software version of physical switch that is capable of forwarding
traffic, VLAN traffic, and so on. The virtual switch is created from
within the Hyper-V Manager and is then
connected to one or more available physical network adapters of the
host machine. The physical network adapters on the host machine are then
connected to physical switch on the network.
As shown in figure 1.3, three VLANs are
created under same virtual switch. The host is then connected to the
physical switch by usually combining the multiple physical network cards
into one also called LAG (Link Aggregation Group) or EtherChannel (Cisco’s implementation of LAG) interface. LAG or EtherChannel combines
the speed of both physical network adapters. If for example we have
two 1Gbps physical network cards, with the use of LAG or EtherChannel,
these are combine into a single 2Gbps network card.
Microsoft’s Hyper-V supports the creation of three different types of virtual switches:
- Internal: - The internal virtual switch can communicate only between virtual machines. A common example is a cluster based system where virtual servers connect with each other through a dedicated network connection. Internal virtual switches do not connect to the physical network infrastructure (e.g switches).
- External: - The external virtual switch can communicate directly with the physical network infrastructure. The virtual switch is used to for the seamless communication between the virtual machines and the physical network.
- Private: - The private virtual switch can communicate between virtual machines and the physical host only (physical hardware server).
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Virtual Deployment Infrastructure (VDI) Deployment with Hyper-V
VDI is a new way of delivering desktops to end users. In VDI,
virtual desktops are hosted centrally as virtual machines and are
provided or streamed to users via the network or Internet using Remote Desktop Protocol (RDP)
service. These virtual desktops can be used or accessed by users with
different types of devices like, PCs, laptops, tablets, smart phones,
thin clients, and so on. VDI have created a new hype of Bring Your Own Device (BYOD) concept. With BYOD
policy implemented in the organization, users can bring their own
devices like laptops, tablets, etc. and the company delivers the
required virtual desktop via the network infrastructure.
VDI is an upcoming trend that offers many advantages such as:
- Central management and control
- Low cost since there is no need of desktop PCs. Alternate devices such as thin clients usually preferred
- Low power consumption. Tablets, thin clients, laptops require low power compared to traditional desktop or tower PCs
- Faster desktop deployments
- More efficient backup
VDI is fully supported and can be implemented in Windows Server 2012 by installing Remote Desktop Services
server role and configuring the virtualization host. You can create
virtual machines running Windows XP/7/8 and easily assign the virtual
machines to users.
We’ve covered a few of the important virtualization features deployable with Windows Server 2012 and Hyper-V, that allow organizations to consolidate their server, network and desktop infrastructure, into a more efficient model.
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