Solid State Storage

After years of the status quo in solid state storage, recent advancements may bring about replacements for conventional hard drives in about five years. One solid state technology, flash memory, has two big weaknesses: It wears out after a relatively small number of writes, and it's slow compared with other types of memory. Future generations of solid state technologies, such as MRAM (magnetoresistive RAM) and phase-change memory, don't have these limitations.

Freescale's commercial MRAM chip is the first of its kind on the market and operates at 4 Mbps. MRAM combines an unlimited write potential and high speed with flash RAM's nonvolatile nature.

Solid state drives may seem like a new phenomenon in storage, but these devices have been around for 25 years. The original market for solid state drives was in military and industrial applications, where the environment was too harsh for standard magnetic hard disks.

The primary markets for solid state drives outside these sectors are for personal use in thumb drives, cameras and MP3 players, as well as in high-performance computing environments where raw speed is important. But technologies like MRAM are not in general use in the enterprise because of the fantastic increase in cost-density-performance ratio of standard magnetic hard-disk technology and the huge density and low cost of flash. The future viability of nonvolatile RAM outside of flash is a concern. Clearly, the consumer and portable markets demand these technologies, but can nonflash technologies reach cost-density levels to make them viable in the enterprise? Solid state drives for enterprise SAN use are composed of battery-backed volatile DRAM (dynamic RAM); there are no devices based on nonvolatile technologies.

The future of nonvolatile RAM technologies is unknown. The cost-density ratios of products are far too low to be considered for enterprise solid state drive deployment, and Freescale's uses for MRAM are largely designed for embedded and hardened systems. It will be five years at the earliest before MRAM or a competing nonvolatile RAM technology will challenge magnetic disk, battery-backed volatile DRAM or flash.

Despite concerns about nonvolatile RAM, its potential is huge both for enterprises and consumers. Corporate laptops, desktops and servers could become truly instant-on devices, where the current state of the device is always in a memory that cannot be flushed by a simple power cycle. Systems could be selectively powered down during nonpeak hours in the data center. And devices such as routers and Ethernet and Fibre Channel switches could benefit from instant-on technology.

The Great DivideThe current solid state drive market is divided between two technologies. The first, flash RAM, is the most easily visible in the market. Nearly everyone has a small USB thumb drive of some sort to make data movement and backup convenient. The second kind of solid state drive is made with standard volatile DRAM technologies, backed up by a battery device. These solid state drives are commonly used by enterprises in the data center to speed up everything from data acquisition to transaction processing to database updates.

Beyond that, there are two dominant physical form factors for solid state drives. The first, drop-in replacements for magnetic hard-disk drives, come in standard hard-drive form factors and are almost always flash-based. Products such as BitMicro's E-Disk series include IDE/ATA or SCSI interfaces and range in size from 2 MB to 155 GB. Memtech also sells drive-compatible flash devices in a variety of sizes and interfaces. And Samsung offers replacement flash drives for laptops. The second form factor is rackmounted boxes that resemble RAID arrays containing battery-backed DRAM. Solid Data Systems, Texas Memory Systems and others assemble solid state devices and offer them with Fibre Channel external, SCSI external or InfiniBand connections. Current models range from 2 GB to 1 TB of storage. These units generally are treated by systems and software as a standard RAID array but contain no actual magnetic disks.

Today And TomorrowNot many enterprises use solid state drives in the data center, though that could change as cost-density factors improve. The potential of solid state drives to increase the performance of enterprise software poises this technology for significant growth. Rather than from flash, the tide of change will come from new nonvolatile memories, such as MRAM or phase-change memory.

Phase-change memory uses the properties of a layer of chalcogenide glass for its electrical-resistance properties and could produce nonvolatile RAM with a density that exceeds even today's hard disks.

Enterprises that aren't using solid state disks should evaluate units if they have an ultra-high-performance transaction application. Keep an eye on the developments in solid state disk technology, looking closely at 2011 when we expect the next generation of high-performance nonvolatile RAM to come to market.

Who's Who

Some of the big players in the nonflash, nonvolatile RAM market are Freescale, Hitachi Data Systems, Intel, Ovonyx, Samsung and ST Microelectronics. But only Freescale has a commercially shipping MRAM product. The rest are developing other types of nonvolatile memory products such as phase-change memory. Ovonyx licenses phase-change technology to all other phase-change memory players including NEC, Sony and Toshiba.There are only a few companies making non-Flash-based, nonvolatile solid state drives, among them Aspacia, BitMicro, Dynamic Solutions International and Texas Memory Systems. One important bellwether of the prominence of solid state drives will be the development of these products by large storage vendors. When EMC, Hewlett-Packard, Hitachi Data Systems, IBM and Sun Microsystems begin to produce large solid state units for enterprise use, RAM-based disks will have arrived. n

Steven J. Schuchart Jr., A Former NWC Technology Editor, Is an analyst for competitive intelligence firm Current Analysis. Write to him at [email protected].