Samsung, Sun tie up to enable flash drive stability

Samsung Electronics has worked with server maker Sun Microsystems to develop a new 8Gbit single-level-cell (SLC) design for computer servers that it claims increases the number of read/write cycles for NAND flash memory chips five-fold.

Solid-state drives (SSDs) are just beginning to gain traction in a variety of computers from laptops to servers. A limit of typically about 100,000 cycles for SLC chips and as little as 10,000 cycles for higher capacity multilevel cell chips has been one of the recent big impediments for adoption. The new chips are expected to support as many as 500,000 read/write cycles and should be available later this year at costs to be determined.

Encouraging flash drives use
Flash drives are starting to be deployed to boost performance and response times in servers and storage systems. The drives consume significantly less power and space than competing hard drives factors that also have driven adoption in notebooks and desktops.

However, flash drives are significantly more expensive than hard disks. Hard drives for PCs cost as little as 36 cents per Mbyte today. By contrast flash drives for PCs cost about $6.65/Mbyte. "The costs for flash drives are expected to decline about 43 percent on a compound basis through 2012," said Jeff Janukowicz, flash drive analyst, International Data Corp.

Many systems adopting flash drives including notebook and desktop PCs and even Web servers, do not require high read/write cycles. However, many of the high performance server and storage systems that want flash drives do need to support the maximum amount of read/write cycles.

Virtual adoption of flash drives
"In June, Sun said it expects to offer flash drives as an option for virtually all its servers and storage systems by the end of the year," said Michael Cornwell, lead technologist for flash memory, Sun, and worked with Samsung on the new chips. The server maker has designed its ZFS file system to take advantage of the fast response times of flash drives that it will use primarily for caching data.

The new Samsung chips are unique because they increase flash read/write cycles dramatically without changes at the controller. Typically to improve endurance vendors applied to flash-subsystem controllers advanced error correction codes and wear-leveling algorithms that ensure work is spread evenly across all NAND cells.

"We did this all at the level of the flash chips themselves," said Cornwell, although he would not elaborate on the techniques used.

Force in server adoption
A Samsung spokesperson said the chips will not be exclusive to Sun but he could not say when they will be available, at what price or how the additional endurance was added.

Cornwell said better interfaces at the level of flash chips and flash drives will be important for driving adoption of the technology in servers. Intel is leading work on the Open NAND Flash Interface that substitutes a typical 40Mbyte/s flash interface with a double-data-rate DRAM interface running at 130Mbps to 400Mbps.

"That will be a big driver for flash drives in enterprise systems," Cornwell said.

A separate effort to develop a controller interface for nonvolatile memory could deliver an improved interface for flash disks. Today's flash disks use a wide variety of interfaces including traditional drive interfaces such as serial ATA, SAS and IDE as well as PCIe.

IDC projects as many as 2.2 million SSDs could ship by 2012 to create a $900-million market. That market today is estimated at about $260 million.

As many as 50 flash drive makers are edging into the market, compared to just seven companies that make hard drives. "There is a lot of R&D investment going into this space right now and a lot of it is going into flash controllers," said Janukowicz.

Indeed, start-up Fusion IO announced in June it is working with Hewlett-Packard's storage group on its proprietary flash controller technology that aims to increase read/write cycles for flash disks.

- Rick Merritt
EE Times