Getting the most out of flash storage

By Gary Orenstein, vice president of product and technical marketing, Fusion-io, Network World |  Storage, flash storage

If you consider flash as a new form of media, like tape and disk drives are media, then implementing it the same way you implemented previous media technologies is only a small part of the way forward.

By itself, flash removes the part of the latency bottleneck caused by slow spinning disk drives, but it does nothing to resolve the delay in getting process-critical data to and from the CPU.

Storing data in a flash array puts process-critical data on the wrong side of the storage channel, far away from the server CPU that is processing application and database requests.

The result is a minimal performance gain and, in addition to adding more hardware, organizations must also implement complex and costly storage area network infrastructure, including host bus adapters, switches and monolithic arrays.

But most importantly, these architectures retain the traditional implementations of storage, as well as RAID, and SATA/SAS controllers -- all optimized to spinning drives, not NAND flash silicon. Figure 2 shows the layers still present in this legacy approach.

The potential

Increasingly, solid-state vendors have recognized that the key to realizing improved performance is putting flash close to the CPU, and they are creating devices that use PCIe natively, without the inhibitors of outdated translation layers.

BACKGROUND: Flash storage moves closer to CPUs

However, some of these devices hamstring performance by placing the flash under the control of legacy storage implementations of SATA or SAS controllers that were initially designed for disks. These protocols and data handling mechanisms were never intended to operate with NAND flash and do not do any justice to NAND flash capabilities. It's like putting a performance automobile engine into the body of a 25-year-old clunker.

The same thing goes for RAID controllers. Initially designed to aggregate the performance of multiple disks and protect from individual disk failures, conventional RAID mechanisms work well for spinning media. However, these mechanisms do not work well for NAND flash, because they inject too much latency.

The best mechanism to place flash in a server is referred to as native PCIe access, where legacy storage technologies are put aside, and a new cut-through architecture provides the most direct, accessible, and lowest latency path between the NAND flash and the host memory.

Originally published on Network World |  Click here to read the original story.
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