Virtualization Tutorial continued

Resource virtualization
The basic concept of platform virtualization, described above, was later extended to the virtualization of specific system resources, such as storage volumes, name spaces, and network resources.

Vmware ESX Server


* Resource aggregation, spanning, or concatenation combines individual components into larger resources or resource pools. For example:
o RAID and volume managers combine many disks into one large logical disk.
o Storage Virtualization refers to the process of completely abstracting logical storage from physical storage, and is commonly used in SANs. The physical storage resources are aggregated into storage pools, from which the logical storage is created. Multiple independent storage devices, which may be scattered over a network, appear to the user as a single, location-independent, monolithic storage device, which can be managed centrally.
o Channel bonding and network equipment use multiple links combined to work as though they offered a single, higher-bandwidth link.
o Virtual Private Network (VPN), Network Address Translation (NAT), and similar networking technologies create a virtualized network namespace within or across network subnets.
o Multiprocessor and multi-core computer systems often present what appears as a single, fast processor.

* Computer clusters, grid computing, and virtual servers use the above techniques to combine multiple discrete computers into larger metacomputers.

* Partitioning is the splitting of a single resource (usually large), such as disk space or network bandwidth, into a number of smaller, more easily utilized resources of the same type. This is sometimes also called "zoning," especially in storage networks.

* Encapsulation is the hiding of resource complexity by the creation of a simplified interface. For example, CPUs often incorporate cache memory or pipelines to improve performance, but these elements are not reflected in their virtualized external interface. Similar virtualized interfaces hiding complex implementations are found in disk drives, modems, routers, and many other "smart" devices.