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    Capacities and Storage Devices

    Some SSD advocates project that SSD price per gigabyte will cross over that of HDDs, due to slower growth in areal density of HDDs in the future than it has grown in the past.  HDD price per GB declines will slow as a result of a slower areal density growth.  The argument is that this would allow flash gigabyte prices to blow past HDD prices just as they slipped below DRAM gigabyte prices in 2004.

     Some of these advocates recently predict that 3.5″ HDDs will “only” reach 6TB by 2015.  Although we find it likely that we will have 6 TB HDDs in mass production by then, Coughlin Associates expects to see 10TB maximum announced product capacity of 3.5-inch hard disk drives by that time. 

     Slower areal density growth of hard disk drives may result from transition difficulties to new recording technologies such as patterned media and heat assisted magnetic recording.  It appears likely that we may see areal density growth slowing from 40-50% annually today to 20% or possibly even less over the next few years.  Today the HDD industry is shipping 2 TB 3.5-inch HDDs and 1 TB 2.5-inch HDDs and will likely ship 3 TB or larger (3.5-inch) drives in the second half of 2010.  If the areal density of HDDs increased only 20% annually from 2010 through 2015 this would give us 7.5 TB 3.5-inch HDDs and over 3 TB 2.5-inch HDDs.

     Although a slow down is likely during a technology transition phase it is likely going to slow down gradually from today’s roughly 40% annual areal density growth rate.  So let’s say we have one more year of 40% growth (2010-2011), one year of 30% growth (2011-2012) and then 20% growth for the three remaining years to 2010.  With a 3 TB capacity in 2010 that would give us a 9.4TB capacity in 2010.  There is enough uncertainty in these numbers that the actual capacity could be between 8 and 11 TB so let’s say the maximum storage capacity in 2010 for 3.5-inch drives is 10 TB.  Likewise because of the geometry differences the maximum 2.5-inch storage capacity would be about 5 TB. 

     If the HDD industry stays true to its history, these 10TB HDDs will cost $50, giving a price per terabyte of $5.  Meanwhile, NAND flash terabyte prices will have declined to $50-100, preventing SSDs from displacing HDDs at least through 2015!

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