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  Virtualization technologies are having a major impact on the design of next-generation datacenters. By de-coupling computing workloads from the infrastructure used to deliver them and supporting multi-tenancy for all major components of the computing environment, virtualization technologies are enabling organizations to develop an infrastructure-as-a-service (IaaS) platform. Put another way, it is the availability of virtualization solutions for servers, storage, networking and many other datacenter resources that is paving the way for today’s organizations to steadily transform their datacenters into private clouds. The result from a technical perspective is the ability to meet the computing requirements for all tenants—applications, business units, operational teams and, in the case of service providers, customers—while minimizing the need for dedicated hardware and specialized systems. From a business perspective, the impact is an unprecedented ability to shrink the datacenter footprint—to consolidate infrastructure and reduce total cost of ownership (TCO)—while significantly improving the performance and reliability of business-critical computing services, as well as the organization’s responsiveness and adaptability to changing business conditions. Maximizing these benefits, however, depends on the availability of virtualization technologies not only for server, storage, and networking resources but also for essential network security and application delivery components.

The value of virtualization primarily derives from two core capabilities:
  1. Abstraction provides deployment flexibility and portability by enabling higher-layer services to be de-coupled from the underlying resources used to deliver them.
  2. Multi-tenancy provides more-efficient utilization and consolidation of resources by enabling a single physical instance of a resource to be shared simultaneously by multiple consumers.
For example, with server virtualization, it is abstraction that enables virtual servers to run different guest operating systems and to be migrated from one physical server to another; whereas multi-tenancy is what makes it possible for a single physical server to run multiple virtual servers at once.

In any case, it is the presence of one or both of these capabilities in a wide range of technologies and related solutions that is providing today’s organizations with a multitude of attractive options when conducting a datacenter buildout. For server/compute infrastructure:
  • Extensive consolidation can be achieved with server virtualization as robust isolation and resource allocation capabilities enable workloads for different tenants to securely and effectively run on the same physical server.
  • Further simplification of datacenter infrastructure is made possible as leading server virtualization solutions enable virtual pools of server resources to be used to efficiently establish enterprise-grade services for high availability, disaster recovery and automatic workload scaling.
  • Unified (or modular) computing platforms that combine
virtualization technology with server, switch and storage modules provide another option for architecting the access layer and achieving yet another degree of physical consolidation. For storage infrastructure:
  • Storage area network solutions eliminate the need for dedicated disks or direct-attached storage.
  • Unified communications fabrics enable convergence of LAN data and storage protocols, thereby reducing the need for a completely separate set of network infrastructure for storage (i.e., adapters, links and switches).
For network infrastructure:
  • Software access switches that run as virtual machines (VMs) or integral components of a hypervisor introduce the potential for completely eliminating the access tier of conventional three-tier network designs, at least from a physical perspective (see Figure 1). (= diagram showing physical topology of conventional 3-tier datacenter network).
  • Alternatives to the Spanning Tree Protocol—such as virtual PortChannel (vPC) technology from Cisco and IETF-TRILL—are enabling a shift from highly scalable Layer 3 network designs to highly scalable Layer 2 networks that are better suited to meeting the performance requirements of a highly virtualized computing infrastructure. This, combined with the availability of high-capacity, non-blocking switches, introduces the potential for “flatter” datacenter designs that do not include a distinct aggregation tier.
  • The availability of virtual device instances for core switching platforms introduces the possibility of both vertical and horizontal consolidation. Vertical consolidation is achieved in the sense that physical aggregation-tier switches can optionally be replaced with virtual instances running on a core switching device. Alternately, or even simultaneously, horizontal consolidation can be accomplished by “absorbing” into the core switching platform any separate switches that might otherwise operate in parallel to it for various purposes, such as to accommodate testing and development, support a newly acquired business unit or isolate one that is being divested.
  • A variety of Layer 2 and Layer 3 technologies such as VLANs, VPNs and virtual routing tables can be used to logically maintain isolation and individualized treatment of different tenants as former physical boundaries are eliminated in favor of physical consolidation and simplification.   t is important to acknowledge, too, that this is only a small sample of available virtualization technologies and possible implementation scenarios. The potential combinations and permutations and resulting physical and logical topologies are actually endless. Combined with the fact that different organizations have different needs, this strongly suggests that no two datacenter designs will ever be exactly the same. The implication is that, going forward, all datacenter solutions—including ADCs—must exhibit a commensurate degree of flexibility enabled by a robust set of virtualization technologies or risk being left behind in favor of alternatives that do.
The benefits of a highly virtualized datacenter Taking a deeper look into the “how” and “why” of datacenter virtualization, most organizations start out by implementing pockets of virtualization technologies across subsets of their tenants. From a tactical perspective, the big draw is the ability to reduce physical footprint and save on equipment costs and datacenter resources such as power, cooling and space. Additional advantages include better application performance, improved reliability, an enhanced user experience and more-efficient IT operations. However, the ultimate goal is to expand, unify and orchestrate these pockets of virtualization to the point that they become a fully functional private cloud. This is because such an approach compounds and maximizes available benefits. For instance, with a highly virtualized datacenter:
  • Maximizing consolidation gains does not come at the cost of organizational rigidity and having to cluster like tenants in specific physical locations.
  • Resources can be scaled based on aggregate rather than per-tenant requirements, further minimizing hardware spend and associated costs.
  • The ability for any set of physical components to support the need of practically any tenant in an on-demand manner streamlines IT operations and enables superior responsiveness to changing business conditions at the same time that it delivers an unmatched degree of adaptability and, therefore, investment protection.

  The need to virtualize other datacenter services Considering the compelling benefits involved it is inevitable that most organizations will embrace a wide array of the previously discussed virtualization technologies to transform their datacenters into private (or hybrid) clouds. IT managers need to realize, though, that there is yet another important piece to the datacenter virtualization puzzle. Specifically, the deployment flexibility and multi-tenancy capabilities enabled by virtualization must be supported for more than just server, storage and networking infrastructure. To truly maximize available gains, similar capabilities should also be present for other key elements of datacenter infrastructure, including ADCs and, although they are not addressed in this paper, network security devices such as firewalls and intrusion prevention systems. It is also imperative that these capabilities be made available in sufficient quantity and variety and for numerous form factors such that the resulting solution set is fully capable of accounting for the broadest spectrum of potential datacenter designs.

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