Vanished: The Line Between Main Memory And Primary Storage: Page 2 of 2

So there are a number of use cases today, but the real implication of flash storage on the memory channel is for the storage industry of the future. I am not given to hyperbole, but memory-channel-attached flash storage is a game changer, a sea change, a paradigm shift, and a revolution. The prevailing paradigm today is shared storage as represented by the storage area network (SAN). Decoupling physical servers from the primary storage they use to access data required by their applications has proven highly successful for both cost and management reasons.

MCS, on the other hand, is a back-to-the-future approach with a twist. When we talk about direct attached storage (DAS) to a physical server, that means the HDDs were attached through an I/O bus of some kind and not on the memory channel itself. HDDs held primary storage, which contains the official production copy of the data. When DAS is moved to the memory channel, primary storage is also moved there. That blurs the distinction between memory and primary storage. In addition, no HDDs need apply as they can never move to the memory channel.

Now, while the MCS is useful for many use cases it is not a complete overall storage environment in the class of a SAN by itself. That requires a number of new capabilities, such as the ability to turn storage capacity across a large cluster of servers into a shared pool of storage (a virtual SAN). A number of options, such as those from PernixData and EMC’s ScaleIO, may be the answer to this. In addition, a number of storage and data management capabilities have to be made available, such as quality of service, multi-tenancy, and data protection.

But why go from a physical SAN to say a virtual SAN when not everyone needs the enhanced performance? In his book “The Innovator’s Dilemma,” Clayton Christensen discusses the concept of “good enough” performance, where performance is any dimension that provides product differentiation. Innovators can introduce disruptions with good enough performance that meets many customers’ needs without having to pay a premium price. The memory channel storage innovation seems to go against Christensen’s concept, in that the focus of this innovation is providing more than good enough performance. However, there are many high-performance requirements today that aren't met cost effectively and therefore the required performance cannot be provided at a “good enough” price.

But note that many applications may not know the value of additional performance, such as for real-time business intelligence, which is the process of delivering information for insight and possible action about business processes as they happen. They may not be able to predict performance requirements and how either planned or unplanned bursts in demand can be handled. Moreover, extra performance by itself is not bad; the bad thing is if you have to pay a premium for it (if sports cars were less expensive, more people would buy them). As cost approaches parity, the increased performance outweighs whatever premium you might pay.

And as I have discussed in previous posts, flash for primary storage may not be more expensive than a hard disk solution. Once price goes out the door as an issue and when management issues are resolved, the move will be to flash and the ultimate move will be to flash on the memory channel.

Mesabi Musings

Main memory and storage have always been seen as distinct, even though they are closely allied in function and form. The innovation provided with in SMART’s ULLtraDIMM form factor module has blurred any distinction.

Main memory can now be primary storage if one wants it to be. Very low, consistent latency can be used for high-performance applications from financial services to big data. But, in the long run, the technology is also a disruptive one to the storage industry as it is a back to a DAS view of the storage universe where servers and their storage are even more tightly coupled than ever, as opposed to the SAN shared storage universe that has proven popular.

As for now, IT teams should focus on the immediate uses and benefits of the Diablo-SMART innovation, but they should also keep their eyes peeled over the course of the next several years as to how the world of the virtual SAN will impact them.

Neither Diablo Technologies nor SMART Storage Systems is a client of David Hill and the Mesabi Group.