Storage in a Virtualized Environment

Renny Shen (Profile)
Wednesday, July 7th 2010


Business in the 21st century is becoming increasingly data-centric. Companies are both creating and consuming growing amounts of data to build more complex products and services, operate rapidly globalizing organizations, and make informed business decisions. The result has been a proliferation of applications and data  that threatens to overwhelm IT organizations. For many, IT budgets and staffing have simply not kept pace.
Server virtualization has emerged as a key technology that allows IT to do more with less – deploy less hardware and increase IT flexibility in provisioning new servers and clients. But server virtualization is also driving changes in how organizations manage their storage, not only increasing the demand for storage capacity but pushing organizations to a virtualized networked storage infrastructure as well. With server virtualization being just the first step in the data center evolution to the cloud, how will storage requirements continue to evolve?

How Server Virtualization Impacts Storage

As with any highly disruptive technology, the cloud will inevitably impact IT infrastructure and processes in ways that cannot currently be foreseen. However, the adoption of server virtualization provides some useful clues. While it is true that server virtualization can lower the costs of the server infrastructure, it can have the opposite effect on the storage infrastructure. Virtual servers often consume more storage capacity than physical ones, and can create additional demand on networked storage.

VM (virtual machine) sprawl is by now a widely observed and well understood side effect of server virtualization. Virtual servers are far easier to provision and deploy than physical ones and the perceived cost is significantly lower when only considering the server hardware that is required. For that reason, enterprises often over-provision the number of virtual servers in their environment and, as a result, have many that are not in active use. However, idle virtual servers still consume the same amount of storage capacity. Furthermore, organizations typically provision capacity for virtual servers from high-performance and high-cost storage resources, which makes VM sprawl both costly and inefficient.

Server virtualization is accelerating the shift to networked storage. Not only are VM images typically stored on networked storage (FC, iSCSI or NFS),  but as more application servers are virtualized, application data will also be increasingly stored on the network. Server virtualization offers the flexibility to dynamically increase or decrease the number of virtual servers running an application to respond to changing demand. Because of this, data created and accessed by virtual application instances must be located on centralized networked storage accessible by any virtual server.

Desktop virtualization has a similar impact, shifting storage consumption from the desktop to networked storage. To maximize the benefits of centralized management, organizations create standardized images for desktops that are then provisioned to users. This creates an incentive to distil the desktop image to the bare minimum and push any custom content such as user data off of the desktop and into the network. Storing user data in network home directories also gives users the ability to access it from anywhere and at any time. However, networked storage is typically much more expensive than desktop storage as it understandably must meet higher requirements for performance and availability.

Storage Virtualization Can Help