Reflections on Storage Virtualization.

One of the best time investments you can make is attendance at the annual Server I/O conference in Monterey, California. Not only is the venue beautiful, but the technical content of the conference, this year focused on data center infrastructure, is worth the admission. Conference organizer and futurist Michael Peterson asked a riveting question at the Storage Virtualization panel. Does virtualization imply or demand interoperability? It sounds like a tale of two buzzwords, but the issue is worthy of reflection.

Storage virtualization, practically speaking, is nothing new. Back in the '60s, it was known as tape emulation, with a clear purpose and application. Modernly, the definition of storage virtualization is more elusive, and it seems to lack a driving application. What storage virtualization does bring to the party, however, is a clear business purpose. Ideally, storage virtualization makes it possible to reduce storage management costs through more effective use of storage resources. This especially applies to SAN management.

Does virtualization demand interoperability? It certainly looks that way. Inserting a virtualization layer in an infrastructure creates a complex island ... an independent island according to Peterson. Islands of storage, however constituted, have never represented cost-effective storage architectures. It could be argued that a virtualization strategy actually works against the storage networking trend in the direction of open standards and heterogeneity. Interoperability problems are typically absent where you are locked into a single vendor's SAN solution. It is for this reason that the overwhelming number of SAN deployments are proprietary. This trend is likely to change as SAN management software gains sophistication and reaches beyond its UNIX-flavor roots to other operation systems, such a Windows. A new company called Netreon is offering such a management package.

Peterson, however, points out a significant trend in virtualization ... it is settling in hardware. The virtualization function could end up embedded at the chip and board level. If this trend proves out, what will become of the software firms dedicated to virtualization solutions? It is likely that they will migrate into storage management services companies, with virtualization offered as one service among many. There are roughly 48 companies that lay claim to storage virtualization, including giants such as EMC and Hewlett Packard. Not all 48 of them will weather the storms as implementation issues abound. The situation is reminiscent of the early days of RAID technology, which spawned any number of startups that vanished through merger, acquisition, undercapitalization, and ultimately commoditization.

Bruce Thompson at InFusion adds another group of caveats when reflecting on virtualization solutions. One caveat: virtualization solutions are intrusive to deploy. He suggests that such solutions do not take legacy configurations into account; changing configurations is a costly proposition. There is often more hardware to install and differing drivers depending on the new configuration. If the objective of virtualization is, in fact, controlling management costs, it might be trading off to capital costs. The actual savings may be quite a ways in the future.

He also noted that there was no clear architectural platform for virtualization. This is a considerable understatement. With no standards in sight, implementations of storage virtualization are as individual as the companies themselves. For some time, EMC, Network Appliance, and the like have offered virtualization at the array or hardware level. Software powerhouse Veritas offers their approach as a host-based implementation. Companies like XIOtech, DataCore, and Falconstor offer virtualization at the network layer, in some cases as a "storage appliance."

In the same way, virtualization can be implemented in-band or out-of-band. In-band virtualization locates the virtualization layer in the data path between the application and the switch. Out-of-band virtualization passes data between the application and the switch on the way to a storage device somewhere on the network. Virtualization management tools are directly linked to the switch or server where the communication drivers reside ... outside the data path to avoid bottlenecks. Compaq's VersaStor is an example of the out-of-band approach.

Several market analysts look at storage virtualization as the next major movement in evolving storage management. And certainly, some major players are engaged in the space. But it could be argued successfully that new generations of SAN management software may fill the need that virtualization seeks to fill ... controlling cost of storage management.

But that is another story.

CTR wants to hear its readers' views on storage virtualization. E-mail [e-mail]