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SSD laptop drives ‘slower than hard disks’

But are 40% more expensive

Solid-state drives (SSDs) are becoming a more frequent storage component in laptops, and are promoted as being faster and more energy-efficient than traditional spinning hard drives. But tests prove that such drives are actually slower than standard laptop hard disks.

Apple's top-end MacBook Air features a 128GB SSD and costs 40 per cent more than a similar model that has a 120GB hard drive. Sony (Sony VAIO TT) and Toshiba (Toshiba Dynabook SS RX1) also sell premium laptops boasting more-efficient SSDs.

Yet, 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, called "random writes".

Apple MacBook Air

As a result, SSDs that were introduced in laptops last year performed at a speed equivalent to a conventional hard drive spinning at 1,000 revolutions per minute. In comparison, the slowest notebook drives today spin at 5,400rpm.

SanDisk now claims that its new flash memory management system, ExtremeFFS, will dramatically improve two of the main weaknesses today in the technology of solid-state drives (SSD).

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 at the 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 were praised 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.

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

One, called Long-term Data Endurance (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 miles-per-gallon (MPG) rating, or the number of miles a set of tyres 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.

The second metric is called "virtual rpm." It would measure the speed of SSDs vs 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.


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