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MemCon panelists ponder challenges of flash SSDs, HHDs in PC, server applications

By Michael Santarini, Senior Editor -- EDN, 7/20/2007

Nonvolatile memory (NVM)-based computing in the form of SSDs (solid-state disk) drives and HHDs (hybrid hard disk) drives may become a primary driver of the NAND flash market and may make obsolete mechanical hard disk drives in mass storage, server, and PC applications. But there are several challenges that NAND, SSD, and HHD vendors will have to overcome to make that happen, according to speakers at a MemCon panel July 17.

The panel, entitled “The Future of Flash in Computing Platforms,” included Y.R. Kim of Samsung Semiconductor, Bob Pierce of Denali Software, Microsoft’s Vlad Sadovsky, and Intel’s Peter Hazen.

“Throughout its history flash has proven to be a disruptive technology to a number of different applications and a number of different industries,” said Intel’s Hazen. “Photography was turned upside down with the virtual replacement of film with flash memory, and as music got digitized, flash-based MP3 players changed the music industry. We are starting to see that with video as well, where you can store video on a gigabyte of nonvolatile memory—4 Gbytes can store an hour of HD. We are going to start to see video move into the mobile space. Then of course the floppy-disk drive was replaced by flash-based USB drives.”

Today, flash appears well on its way to becoming a disruptive technology in PC storage, as well. Indeed, today NAND densities have increased to a level where they even hold promise to replace magnetic hard-disk drives in traditional storage applications such as personal computers. Vendors have already made a beachhead by offering SSDs and HHDs. “Where we are today is the price for a gigabyte of flash, along with the increasing disparity between faster processing speeds and mechanical latency of hard-disk drives, is presenting an opportunity for NAND to find its way into both client and server computing platforms,” Hazen said. “There are many ways that flash can enter the platform and ultimately it will come down to the value proposition we deliver to the end user for the various types of solutions.”

Panelists said on the surface NAND flash appears to be very promising for use as a hard-disk drive replacement in PC applications because it has a smaller size than HDDs, drains less system power, emits less heat, and is not mechanical, thus subject to mechanical failure.

Hazen predicted that SSDs will find their way into high-end servers and the high-end mobility space (notebook/laptop PCs that require longer battery life), where the user will pay a premium for the attributes of ruggedness, reliability, and performance benefits of solid-state drives. He believes that the first opportunity for nonvolatile memory in the mainstream notebook market will be as a cache, where notebooks will store their most commonly used data in speedy flash-based cache to enjoy the performance benefits of NAND, over hard-disk drives. He also predicted that the lowest-priced SSDs will soon make their way into low end laptops, if vendors can bring the prices of SSDs down below hard-disk drives.

“In high-end servers we care most about managing performance, IOPS or IO per second, the latency to store and retrieve a file,” said Hazen. “Today that’s done through parallelism of a lot of hard-disk drives. I think SSD will find its role in there.”

Today NAND-based SSDs and HHDs typically cost more than HDDs, and vendors have not yet adequately addressed NAND wear issues—that is, there are only so many times a NAND device can write and read data reliably. And at process geometries of 45 nm and below, performance of NAND is no longer increasing.

Samsung’s Kim said SSD capacity is not a huge problem, as SSDs come with capacities up to 64 Gbytes. “The big question is how can we break the price point that is showing a significant gap between hard disk drives and solid state disk drives?” said Kim. Indeed, expect to pay roughly a $300 to $500 premium for SSDs over a hard drive of a similar capacity.

Sodovsky predicted that the reliability of SSD over hard drives in laptops will more than justify the costs for corporations to make the move. “Hard drives are the second largest generator of calls to technicians,” said Sodovsky. “If you measure the number of calls technicians have to make and calculate the hourly wages, laptops will become solid state.”

Bob Pierce of Denali Software conceded that price is the biggest factor in the consumer PC market but he predicts consumers will be willing pay more as laptop makers take advantage of SSD advanced features and performance. “Today’s technology does not take full advantage of flash technology,” said Pierce. “The next step is to say what do I want in this technology to make it better.” Pierce suggested that NAND’s speed advantage holds promise in allowing instant-on boot up of laptops (the laptop will boot faster than with hard disk based devices), which potentially means users won’t have to keep their laptops in hibernate.

Panelists said that cost savings of SSDs in terms of power and heat (cooling) in server applications make SSDs a compelling buy for corporate server applications, as SSDs will cut down power bills and cooling requirements for mass storage applications (conceding top capacity of SSD’s isn’t quite there yet).

But SSDs and especially the NAND devices from which they are composed are not bulletproof and are susceptible to wear issues. [Editors note: It is widely known that NAND devices have write wear issues, but in an earlier article, Intel told EDN that it has conducted studies showing NAND reads also have wear issues.] To combat wear, SSDs contain distribution algorithms that arbitrate the number of reads and writes to NAND devices. Panelists proposed that future SSDs could include meters that monitor each device’s read and write count to essentially forewarn users when they need to start worrying about swapping out chips or drives.

Panelists also noted that while flash devices manufactured in process geometries of 45 nm and below are increasing in capacity, the speed of the devices is not increasing. Hazen says that even if flash vendors don’t figure out a way to increase the performance of the devices, SSD vendors can use parallelism, much in the same way hard disk drive vendors have done for years, to speed up the performance of SSDs.

Despite these issue,s panelists predict that it’s only a matter of time before Flash will once again prove itself a disruptive technology. This time it will be in your PC, rather than something you tack onto it.