Data Center Virtualization
Cloud Computing Applications
Network virtualization may be the most ambiguous, specific definition of virtualization. For brevity, the scope of this discussion is relegated to what amounts to virtual IP management and segmentation. A simple example of IP virtualization is a VLAN: a single Ethernet port may support multiple virtual connections from multiple IP addresses and networks, but they are virtually segmented using VLAN tags. Each virtual IP connection over this single physical port is independent and unaware of others’ existence, but the switch is aware of each unique connection and manages each one independently. Another example is virtual routing tables: typically, a routing table and an IP network port share a 1:1 relationship, even though that single port may host multiple virtual interfaces (such as VLANs or the “eth0:1” virtual network adapters supported by Linux). The single routing table will contain multiple routes for each virtual connection, but they are still managed in a single table. Virtual routing tables change that paradigm into a one:many relationship, where any single physical interface can maintain multiple routing tables, each with multiple entries. This provides the interface with the ability to bring up (and tear down) routing services on the fly for one network without interrupting other services and routing tables on that same interface.
As another example of a tried-and-true technology that’s been dubbed “virtualization,” storage virtualization can be broken up into two general classes: block virtualization and fi le virtualization. Block virtualization is best summed up by Storage Area Network (SAN) and Network Attached Storage (NAS) technologies: distributed storage networks that appear to be single physical devices. Under the hood, SAN devices themselves typically implement another form of Storage Virtualization: RAID. iSCSI is another very common and specifi c virtual implementation of block virtualization, allowing an operating system or application to map a virtual block device, such as a mounted drive, to a local network adapter (software or hardware) instead of a physical drive controller. The iSCSI network adapter translates block calls from the application to network packets the SAN understands and then back again, essentially providing a virtual hard drive.
Cloud computing comes into focus only when you think about what IT always needs: a way to increase capacity or add capabilities on the fly without investing in new infrastructure, training new personnel, or licensing new software. Cloud computing encompasses any subscription-based or pay-per-use service that, in real time over the Internet, extends IT's existing capabilities.
Cloud computing is at an early stage, with a motley crew of providers large and small delivering a slew of cloud-based services, from full-blown applications to storage services to spam filtering. Business leaders are using the cloud within their enterprise data centers to take advantage of the best practices that cloud computing has established, namely scalability, agility, automation, and resource sharing. By using a cloud-enabled application platform, companies can choose a hybrid approach to cloud computing that employs an organization's existing infrastructure to launch new cloud-enabled applications. This hybrid approach allows IT departments to focus on innovation for the business, reducing both capital and operational costs and automating the management of complex technologies.
