What is Virtualization?

Virtualization Pros and Cons

Pros

Affordable disaster recovery
Data center footprint reduction (e.g., space, energy, cooling)
Fast system provisioning (e.g., from months/weeks to days)
Hardware lock-in escape
High physical resource utilization (e.g., from 5-7% to 50-70%)
Near-zero maintenance downtime (thanks to live migration technologies)
- Transparent hardware replacement

Cons

Investment in capacity management (for dynamic, large-scale virtual infrastructures only)
ISVs limited support (e.g., Oracle)
Partially market immaturity
High price for software platforms (e.g., VMware) and hardware infrastructure (e.g., SAN)
High risk of virtual machine sprawl

Virtualization Definitions

According to Wikipedia

Virtualization in computing, is the creation of a virtual (rather than actual) version of something, such as a hardware platform, operating system, a storage device or network resources

Virtualization can be viewed as part of an overall trend in enterprise IT that includes autonomic computing, a scenario in which the IT environment will be able to manage itself based on perceived activity, and utility computing, in which computer processing power is seen as a utility that clients can pay for only as needed. The usual goal of virtualization is to centralize administrative tasks while improving scalability and work loads.

According to Gartner

IT virtualization is the abstraction of IT resources in a way that masks the physical nature and boundaries of those resources from resource users. An IT resource can be a server, a client, storage, networks, applications or operating systems. Essentially, any IT building block can potentially be abstracted from resource users.

Abstraction enables better flexibility in how different parts of an IT stack are delivered, thus enabling better efficiency (through consolidation or variable usage) and mobility (shifting which resources are used behind the abstraction interface), and even alternative sourcing (shifting the service provider behind the abstraction interface, such as in cloud computing). A key to virtualization is being able to effectively describe what is required from the resource in an independent, abstracted and standardized manner.

In essence, cloud computing is all about abstracting service implementation away from the consumers of the services by using service-based interfaces (in other words, the interface for cloud-computing services is all about virtualization — an abstraction interface). But, to a provider, virtualization creates the flexibility to deliver resources to meet service needs in a very flexible, elastic, rapidly changing manner. The tools that make that happen could be virtual machines, virtual LANs (VLANs), or grid/parallel programming.

Virtualization Approaches

Platform virtualization approaches:

Application Virtualization
OS Virtualization
Hardware Virtualization

Resource virtualization approaches:

I/O Virtualization
Network Virtualization
Storage Virtualization
Workspace Virtualization

Virtualization Use Cases

Centralized desktop management (e.g., through client hypervisors)
Desktop consolidation (i.e., Virtual Desktop Infrastructure - VDI)
Disaster recovery
Infrastructure-as-a-Service (IaaS) cloud computing
Server consolidation

Virtualization Market Footprint and Shares

Hardware Virtualization Market Footprint in 2010, according to Gartner:

10.8M virtual machines
23% of installed applications run in a virtual machine

Source: eG Innovations

Hardware Virtualization Market Footprint in at 4Q2009, according to IDC:

$447M worldwide virtualization software revenue
38% of all virtualization hosts shipments led by HP, followed by Dell (28%) and IBM (15%)
19% YOY licensing revenue growth for VMware. Microsoft growth 215% YOY. Citrix growth 290% YOY.

Source: IDC

Hardware Virtualization Market Share in 2010, according to Gartner: