The last few entries we have been covering aspects of unified storage. The bottom line is that unified storage has it's place and many organizations can benefit by having these systems, but where does this leave storage platforms that essentially do one thing and do it well?There are examples throughout the various storage categories SANs, for example like those from 3PAR or Compellent which have fibre and iSCSI built in and Dell's EqualLogic storage is iSCSI only. In all three cases they are as easy to use as most unified platforms and NAS can be added via a gateway like ONStor's or even a Windows Storage Server. The unified camp will say that is their weakness, that you have to manage the NAS through a separate interface. That is a fair accusation, but for your environment it may not be a deal breaker. Most data centers will always have more than one storage platform, managing NAS services separately may not be a huge burden for you.

For this theoretical trade-off you often benefit with unique capabilities. Dell and 3PAR both offer via different methods a unique scale-out capability that maintains performance as the platform grows. 3PAR also includes specialized silicon to optimize its cornerstone thin provisioning capabilities. As we discuss in our article on "Keep Thin Provisioning Thin", advancing the state of the art of thin provisioning is going to require partnering with companies like Symantec to leverage Thin API's at the file system level and it may require specialized hardware to bring advanced thin provisioned volumes without impacting performance.

Network Attached Storage (NAS) is where unification really began and most NAS vendors now offer some block protocol support typically via iSCSI, a few like BlueArc and Isilon are still mostly focused on the file system side of the business. BlueArc for its focus has delivered high performance and a suite of file management tools while Isilon has focused on building a scale out architecture that can offer linear performance or high density.

Focus gets these companies to where their competition wants to be faster, in some cases years. The linear performance offered by clustered storage is a great example, almost every major manufacturer has expressed a desire to offer products in this category yet the companies that have focused on it have been delivering them for years. In our article "Searching for High Performance Storage" we explain the challenges involved in maintaining storage performance as the environment scales. This is an issue for many companies and with the continued growth in server virtualization, an increasing number of companies will need scalable storage IO.

What's better, to have two storage platforms, one focused on block IO and the other on file IO, or to have a single unified platform but deal with either additional systems as your storage capacity and performance demands grow? Part of the answer depends on how quickly and how often you will need to add that capacity and performance.

If the only constant in your environment is an ever increasing demand for capacity and performance then the linear scale of a cluster, even if it is in two pods (NAS and SAN) might be better. If the demands of the system you can afford today more than meet your needs for performance and capacity then a unified system may be more cost effective and potentially easier to use.

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George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.