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The rise of SSDs over hard drives, debunked

Lucas Mearian | June 24, 2015
In spite of a recent report to the contrary, solid-state drives (SSDs) will not surpass hard disk drives (HDDs) in either price or capacity any time soon, according to industry analysts.

Flash makers have also increased the number of bits -- from one to three -- that can be stored per NAND flash cell, all of which has increased density and reduced manufacturing costs.

Today, multi-level cell (MLC, or two bits per cell) and triple-level cell (TLC, or three bits per cell) NAND flash dominates the market.

More recently, the same flash makers have introduced three-dimensional architectures that allow layers of NAND flash to be stacked atop each other like a microscopic skyscraper. Samsung started the trend with a 32-layer chip it called V-NAND. Toshiba then followed with a 48-layer 3D flash memory called BiCS (Bit Cost Scaling).

The result of the technological advances is a 16GB chip that can be used to produce high capacity SSDs that today offer 4TB of capacity for consumers and will likely be knocking on 8TB and 10TB in the near future -- perhaps even by the end of the year.

For example, SanDisk hopes to release an 8TB SSD this year. Manuel Martull, SanDisk's product and solutions marketing director, has said the company hopes to continue doubling SSD capacity every one to two years, vastly outpacing traditional HDD capacity growth.

The advances in NAND flash density that have some writing that SSDs will reach price parity with HDDs, a claim that experts balk at.

Of all the NAND flash makers, only Micron and Intel have publicly discussed a 32GB (3D MLC) and 48GB (3D TLC) chip, both of which are 32 layers deep. But even that memory would not be 32 or 64 times the capacity todays NAND flash dies. Even a 128GB single die (1Tbit) chip would only be eight times the density increase over today's chips, according to Gartner.

"There's a stupefying quantity of hogwash out there," said John Monroe, vice president of research for data center systems at Gartner. "HDD makers are forecasting a 20TB 2020; my guess is the [manufacturer] cost would be around $175 per drive.

"In 2020, let's assume a cost of $0.11/GB for a 25TB SSD, that would be $2,750 manufacturer cost per drive," Monroe added.

Today, even computer manufacturers who buy SSDs en masse are paying on average about $50 for a 128GB SSD. If a consumer were to spend $50 on an internal hard disk drive today, they'd walk away with 1TB of capacity.

And, when it comes to data center class SSDs, on average the price per gigabyte of capacity is still nine times higher than HDDs, according to Fang Zhang, a senior storage analyst at IHS research.

"I would agree that SSD vendors will eventually be able to cram more capacity per form factor [than hard disk drives] but this is not the same as price per gigabyte," Zhang wrote in an email reply to Computerworld.


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