Hot Spots: Tap virtual servers, storage for all they're worth


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I/O obstacles could throw a monkey wrench into virtual server environments, but there are alternatives to traditional methods.

It's no secret that virtualization services are proliferating in the data center. Server virtualization has become one of the most significant agents of change in today's IT shop. In addition to enabling far greater server utilization rates, this technology offers corresponding power and cooling benefits that many IT organizations find attractive. In response to successful server virtualization efforts, many companies are now developing storage virtualization products that offer single pools of storage, thin provisioning and snapshot to create similar efficiencies.

To take full advantage of server virtualization benefits like app mobility and high-availability/disaster recovery (HA/DR) capabilities, virtualized servers need networked storage. According to a recent ESG research report, "Server Virtualization: The Impact on Storage," 86% of respondents using server virtualization support their virtualized environments with networked storage, and the majority of those are Fibre Channel (FC) SANs. The result is a highly dynamic infrastructure in which every server device requires connectivity to every storage device to ensure flexibility and mobility. However, the I/O path is still being provisioned as it would be in a fixed, nonvirtualized environment.

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To keep pace with changes in the server and storage domains, organizations need to ensure that the I/O path is not a bottleneck.

Major drawbacks to today's I/O model
I/O provisioning has remained largely unchanged in the last 10 years. Network interface cards (NICs) are required to provision IP connectivity, while host bus adapters (HBAs) provision FC access to servers. The technology has advanced--increasing in both speed and intelligence--but it still hasn't managed to keep pace with rapidly changing virtualized environments.

One of the most obvious issues with this type of arrangement is the cost associated with deploying and maintaining an environment that, in a high-availability configuration, will sport two NIC cards and two HBAs per server, in addition to all of the cabling that goes with it.

Troubleshooting an environment with multiple connections becomes difficult because each path may be a point of failure. Some of the most difficult problems to track are related to cables. It's not uncommon for IT staff to spend days trying to troubleshoot a problem only to find that it can be traced to a cable with an extreme bend in it.

There's also the complexity inherent in provisioning new physical servers in enterprises with separate networking and storage groups, both of which need to coordinate to provision NIC and HBA cards. In some cases, this could take weeks.

Traditional HBAs can't see virtual machines, which creates potential security and management issues. From a security standpoint, all applications running on a physical server must be in the same zone. From a management standpoint, it's difficult to tie applications to the storage if you can't identify the virtual machines. Ultimately, you need a better solution for greater scale and flexibility, and improved functionality.

This was first published in March 2008

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