Array Controller-Based Virtualization


Array manufacturers may seem odd bedfellows with switch- makers , given their stake in virtualization as a function of controller design. After all, much of what is taken for storage virtualization architecture today is drawn from the designs of high-end array controllers.

The inefficacies of host software-based RAID in the late 1970s and early 1980s gave rise to the development of hardware-based implementations of RAID technology and led to the rise of a cadre of recognized storage centric vendors that today are household words in the industry. EMC Corporation and others dedicated substantial resources to adding value to their boxes of increasingly commodity disk drives by adding intelligence to controllers. Virtualization (a.k.a. LUN aggregation) arose from direct access storage device (DASD) development efforts at IBM, EMC, Hitachi Data Systems and elsewhere throughout the 1980s and 1990s.

In the process, each vendor developed proprietary approaches arguably intended not only to enhance value to their customers, but also to lock their customers into their products solely. Today, controller-based virtualization achieves its greatest level of sophistication and value if a customer uses only the arrays of a single vendor. By extension, and as a consequence of proprietary technology, Fibre Channel SANs work best only if the storage arrays that they interconnect to servers are homogeneous ”all purchased from one vendor (or a certain cadre of vendors who have exchanged sufficient technology to work and play well together).

The openness of SANs is a myth for as long as proprietary array architecture precludes the virtualization of arrays across vendor boundaries. This is the essence of the teaching derived from a SAN vendor interview cited in Chapter One. The fellow posed the question, "Do you really believe that an open SAN will ever make its way to market? An open SAN would move intelligence from proprietary array controllers to the network itself ”probably onto the switch. People would get the same performance from a JBOD as they would from a high-end array from EMC. They would realize very quickly that they had been paying way too much for storage. Do you think that EMC or any other large array manufacturer would ever let that happen?" [6]



The Holy Grail of Network Storage Management
The Holy Grail of Network Storage Management
ISBN: 0130284165
EAN: 2147483647
Year: 2003
Pages: 96

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