Question: What is the physical weight of one gigabyte of memory/storage? Lets say this is on a hard disk.
What is the weight associated with the atoms that are actually storing the data on the disk? ?How has this value changed as densities of disks have increased?
Answer: Hard drive density is measured in bits per square inch, the highest of which are currently (5/2013) 750 gigabits per square inch. ?This means that a gigabyte of data will take up about 6.88 millimeter2. ?The weight of an area of a platter consists of the substrate (usually glass and ceramic) and the magnetic layer which actually holds the magnetic grains storing the data. ?The magnetic layer is usually made of a mostly cobalt alloy of 10-20 nm thickness. ?Assuming 10nm thickness to make the math easier, This gives us about 6.88 * 1013 nm3 of magnetic layer material for one gigabyte.
Given the density of cobalt, this means that we can approximate the weight at 0.612471 micrograms.
I’m not sure how much the substrate weighs, but it’s almost certainly more than that. ?
2012 Update: This is all about drives that are shipping now – there is a lot of buzz about Seagate getting to 1 terabit per square inch recently, but that is a tech demo and not shipping quite yet.
2013 Update: It looks like the areal density of Hard Drive platters is stagnating, according to an interesting IBM report on the subject of Areal density. ?TDK says that they can approach the 1.5Tbits/inch2 mark, but they won’t show up in the market until 2014. ?The Seagate tech touted in last year is supposed to show up in 2014 as well. ?Next year should be exciting for the weight of gigabytes.
Previously on “How much does a gigabyte weigh on a hard disk?”
- 2009: Areal Density 400 Gbit/in2 = 1.1518 micrograms (ref)
- 2010: Areal Density 541.4 GBit/in2 = 0.84817 micrograms (ref)
- 2011: Areal Density 625 GBit/in2 = 0.734966 micrograms (ref)
- 2012: Areal Density 744 GBit/in2 = 0.617411 micrograms (ref)