Dale & Lewis Chapter 5 Computing components A brief on scales in hard disk drives (HDDs)

Evolution of the HDD IBM Ramac – 5 MB (1956) Hitachi Microdrive – 8 GB (2006) HGST He6 – 6 TB (2013)

Areal density roadmap

HDD x 1,000,000 – a sense of scale 1bit = 1 finger (1.5 × 8cm) Read-write Head Components = Boeing 787 Fly O.D. = 7200 rpm × 300 km = 0.12 c (c=3x10 8 m/s) HDD × 1 million = “a Boeing 787 flying at 12% of the speed of light (at disk’s O.D.) 5mm above a 95 km wide disk and seeking, reading and writing bits of information the size of a human’s finger” HDD × 1 million = “a Boeing 787 flying at 12% of the speed of light (at disk’s O.D.) 5mm above a 95 km wide disk and seeking, reading and writing bits of information the size of a human’s finger” Disk = Mississauga to Scarborough (95 km dia) Fly height = 5mm  Fly height  5mm 95 km 7200 rpm 300 km circumference I.D. O.D. 10 km

Today – 700 Gb/in 2, HMS~8-10 nm, BL~15 nm  1bit = 1 finger (1.5 × 8cm) 7000 rpm 300 mm circumference 95 mm Magnetic Recording Medium disk bit length ~ 15 nm bit width ~ 80 nm grain pitch ~ nm averaged transition width ~ nm  only 5-8 atoms … 1bit  15 grains Fewer than 9 grains contribute to storing value of a single bit. Fewer than 6 grains contribute to read out pitch  8nm Top view