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It may seem as if storage technologies are a little stodgy and out of date, but there’s plenty of technical development going on at both big storage vendors and smaller upstarts.

The enterprise data storage industry doesn’t have a reputation as a hotbed of innovation, but that characterization may be unfair. Although bedrock technologies like RAID and SCSI have soldiered along for more than two decades, new ideas have flourished as well. Today, technologies like solid-state storage, capacity optimization and automatic tiering are gaining prominence, and specialized storage systems for virtual servers are being developed. Although the enterprise arrays of tomorrow will still be quite recognizable, they’ll adopt and advance these new concepts.

Solid-state cache

Spinning magnetic disks have been the foundation for enterprise data storage since the 1950s, and for just about as long there’s been talk of how solid-state storage will displace them. Today’s NAND flash storage is just a decade old, yet it has already gained significant traction thanks to its performance and mechanical characteristics. Hard disk drives (HDDs) won’t go away anytime soon, but NAND flash will likely become a familiar and dependable component across the spectrum of enterprise storage.

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Hard disks excel at delivering capacity and sequential read and write performance, but modern workloads have changed. Today’s hypervisors and database-driven applications demand quick random access that’s difficult to achieve with mechanical arms, heads and platters. The best enterprise storage arrays use RAM as a cache to accelerate random I/O, but RAM chips are generally too expensive to deploy in bulk.

NAND flash memory, in contrast, is just as quick at servicing random read and write requests as it is with those that occur close together, and the fastest enterprise NAND flash parts challenge DRAM for read performance. Although less expensive, flash memory (especially the enterprise-grade single-level cell [SLC] variety) remains an order of magnitude more costly than hard disk capacity. Growth in the deployment of solid-state drives (SSDs) has slowed and isn’t likely to displace magnetic media in capacity-oriented applications anytime soon.

Flash memory has found a niche as a cache for hard disk drive-based storage systems. Caching differs from tiered storage (see the section on “Automated tiered storage”) in that it doesn’t use solid-state memory as a permanent location for data storage. Rather, this technology redirects read and write requests from disk to cache on-demand to accelerate performance, especially random I/O, but commits all writes to disk eventually.

Major vendors like EMC Corp. and NetApp Inc. have placed flash memory in their storage arrays and designed controller software to use it as a cache rather than a tier. NetApp’s Flash Cache cards use the internal PCI bus in their filers, while EMC’s Clariion FAST Cache relies on SATA-connected SSDs. But both leverage their existing controllers and expand on the algorithms already in place for RAM caching.

Avere Systems Inc. and Marvell Technology Group Ltd., a couple of relative newcomers, take a different tack. With a history in the scale-out network-attached storage (NAS) space, Avere’s team developed an appliance that sits in-band between existing NAS arrays and clients. “No single technology is best for all workloads,” said Ron Bianchini, Avere’s founder and CEO, “so we built a device that integrates the best of RAM, flash and disk.” Bianchini claims Avere’s FXT appliance delivers 50 times lower access latency using a customer’s existing NAS devices.

This was first published in August 2011

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