Gartner Research: Planning a Private Cloud?

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The migration to server virtualization and the evolution to private clouds require agile workload provisioning and large virtualized server resource pools for workload mobility. Traditional network solutions will inhibit private clouds if network architects are unable to meet these requirements.


  • Private cloud solutions require network architectures and operational agility that network architects can't deliver via traditional data center networks.
  • Network fabrics have been introduced to improve network architecture, but they constrain virtual server resource pooling, and they do not offer network managers sufficiently improved operational agility.
  • Software-defined networking (SDN) is emerging with the promise of flexible workload mobility as well as programmatic configuration and control, which will assist network architects in meeting the needs of private clouds better than traditional alternatives.


  • Network architects should design the data center network architecture based on the planned use of live virtual machine (VM) mobility and the number of servers within a mobility domain.
  • Network architects that need to support private cloud solutions must move to new network architectures that support VM mobility and orchestration, which may require new software, new hardware, or a new vendor.
  • Network architects should plan to use switch clustering and network fabrics to enhance traditional hierarchical designs for any short-term need to improve network support of VM mobility within the mobility domain.
  • Network architects should begin to acquire knowledge about SDN and vendors' road maps, and should plan for SDN to be a vital component of the enterprise private cloud solution, with mature products available within the next three years.


The introduction of server virtualization, dynamic server resource management via VM mobility and the emergence of private cloud solutions are, at best, difficult to manage with traditional network solutions. Server Virtualization has already been the source of the most significant impacts on the data center network in recent time, but it is only the starting point. As outlined in "The Road Map From Virtualization to Cloud Computing," server administrators typically introduce server virtualization to cost optimize their compute resources. Virtualization creates a pool of manageable and flexible server capacity that makes it possible to optimize resource utilization by moving workloads between physical resources. The management of this server resource pool can be highly automated, and thus become an enabler of agile private cloud solutions.

The key problem for network architects is that existing data center networks can't easily support the evolution to such private cloud solutions, especially in three key areas:

  • Virtualization views physical servers as one very large virtualized resource pool where workloads can be moved freely to enable efficient server resource management and resilience, but it requires very large virtual LANs (VLANs), leading to network instability.
  • VM mobility is a key function for server resource management, but moving workloads creates high-volume traffic between servers. Existing data center networks are not designed for this, and thus lead to network congestion and performance issues.
  • The ability to provision new applications and new virtual workloads in seconds is not easily supported by the highly static provisioning and configuration available in current networks.

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