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SanDisk claims new SSDs will raise speed, endurance

ExtremeFFS will improve two weaknesses in solid-state drives, company says
  • Eric Lai (Computerworld)
  • 07 November, 2008 08:26

SanDisk on Wednesday announced a new flash memory management system called ExtremeFFS that it says will dramatically improve two of the main weaknesses today in the emerging technology of solid-state drives (SSDs).

ExtremeFFS should boost the speed of writing common types of data to SSDs by as much as 100 times, said Don Barnetson, senior director of marketing for the Milpitas, Calif., memory maker's SSD business unit. ExtremeFFS also allows data to be written to disk without erasing and rewriting nearby stored data, Barnetson said. That, along with the ability to move data around to ensure that the physical memory blocks wear out evenly, should boost the longevity of SanDisk SSDs introduced next year, he said.

The first generation of SSDs garnered praise for using less power and generating less heat. But despite claims that SSDs were faster than mechanical spinning hard drives, many customers found SSDs performed slower than conventional disks, especially when writing data.

Barnetson agreed. While SSDs are fast at writing large files and at reading either large or small files, they tend to be far slower than mechanical hard drives at storing small slices of data, what Barnetson called "random writes."

As a result, SSDs that were introduced in notebook computers last year performed at a speed equivalent to a conventional hard drive spinning at 1,000 revolutions per minute (RPM), Barnetson said. The slowest notebook drives today spin at 5,400 RPM.

A push for standards

To help overcome lingering customer concern over SSD performance and endurance, SanDisk also proposed the industry adopt two easy-to-understand metrics.

One, called Longterm Data Endurance, or LDE, would measure the total amount of data that can be written to an SSD before it fails.

For instance, a drive with an LDE of 40 TBW (terabytes written) should be able to last almost 11 years if the user writes an average of 10GB per day.

LDE would be an average figure, similar to a car's mile per gallon (MPG) rating, or the number of miles a set of tires are expected to last, Barnetson said. Vendors are free to tout a lower-range LDE for warranty or guarantee purposes, he added.

SanDisk has already submitted a proposal to JEDEC, which develops standards for the SSD industry.

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The second metric is called virtual RPM. It would measure the speed of SSDs versus conventional hard drives by averaging the faster read times with slower write times.

That's because SSDs working with most PC operating systems, such as Windows, tend to read and write data in a 50:50 proportion, Barnetson said.

SanDisk is also supporting the adoption of a third industry metric that would bolster LDE by helping SSD makers give real-time wear data to users.

While LDE is like the tire's rated number of miles, this would be like "taking a coin to see how much tread is actually left on the tire," Barnetson said.

It would be similar to the SMART spec used by conventional hard drives to measure the health of spinning hard drives, Barnetson said. SMART has been criticized as unreliable because it cannot predict when a drive might suddenly fail due to mechanical problems or shock. But since SSDs are known to be less vulnerable to such types of failures, this specification would be far more accurate, he said. And it could be very helpful for IT managers who have thus far been shy about replacing spinning drives with SSDs due to failure fears, he said.

SanDisk is proposing this specification to the T13 technical standards committee, Barnetson said.

Stephen Weinger, marketing manager for NAND Flash products at rival Samsung Electronics, declined to comment on SanDisk's proposals.

Samsung last month pulled its unsolicited US$5.85 billion offer to buy SanDisk, citing a lack of progress and worsening business conditions.