IBM Systems Technology Group Disk Drive Science IBM

IBM Systems & Technology Group Data Storage through the ages… § Today we store data on computer disk drives § Previously we used writing on paper § Before that, marks on clay § What did mankind use for data storage before the invention of writing? Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group …Grandmothers § § § Data capacity ~ 100 MB ? Data rate ~ 10 b/s Error rate ? Reliability ? Manufacturing cost ? Maintenance cost ? Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Agenda § Demand for disk storage § What drives areal density? Aerodynamics Magnetic recording § Future storage technologies N Soton. ac. uk 2004 | Disk Drive Science | S © 2004 IBM Corporation

IBM Systems & Technology Group Magnetic disk vs. DRAM Soton. ac. uk 2004 |

IBM Systems & Technology Group Disk Capacity Demand Who needs all this stuff anyway?

IBM Systems & Technology Group CERN LHC § 50 yrs, pure research, technology (NMR, PET, X-ray imaging, WWW) § 27 km tunnel, 100 m below FR/CH § 14 Te. V hadron collider § Scheduled start April 2007 § Storage requirements: 109 events / sec 1 PB/s raw data rate Hardware filtering to 100 MB/s 1 PB/yr By 2008, 15 PB/yr § Generate approx 1% of world data production Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Disk drive capacity - definitions §B § KB § MB § GB § TB § PB § EB § ZB § YB Byte Kilobyte Megabyte Gigabyte Terabyte Petabyte Exabyte Zettabyte Yottabyte Soton. ac. uk 2004 | Disk Drive Science | = = = = = One letter or number “A” 1000 B (~ few line e-mail) 1000 KB (~ Bible or Qu’ran) 1000 MB (~ human genome) 1000 GB (~ Books, annually) 1000 TB (Large companies) 1000 PB (Human knowledge) 1000 EB 1021 B 1000 ZB 1024 B © 2004 IBM Corporation

IBM Systems & Technology Group Driving Areal density 5 decades of refinement | March

IBM Systems & Technology Group Inside the head-disk enclosure Soton. ac. uk 2004 |

IBM Systems & Technology Group Disk Drive Basics Soton. ac. uk 2004 | Disk

IBM Systems & Technology Group Aerodynamics “Cruising at an altitude of 0. 000001 feet”

IBM Systems & Technology Group Actuator Assembly - close up Soton. ac. uk 2004

IBM Systems & Technology Group Head / Disk interface Tiny air gap! ~0. 0000000200 m (200 nm) Slider (Ferrite, Fe/Silicate glass) Head Disk Coating (Ni. Cr. Mo alloy + 3 atoms Ru) Disk Substrate (Aluminium or Glass) Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Evolution of flying height Soton. ac. uk 2004 |

IBM Systems & Technology Group The Slider Soton. ac. uk 2004 | Disk Drive

IBM Systems & Technology Group Managing flying height Demo (if it works) | March

IBM Systems & Technology Group Disk Surface Preparation Full Surface Texture Zone Texture Head / Slider Dedicated landing zone No Texture Soton. ac. uk 2004 | Disk Drive Science | Smooth data zone Ramp or lift mechanism © 2004 IBM Corporation

IBM Systems & Technology Group Disk Aerodynamics - summary § Slider “flies”over the disk surface § (but very close) § “Air Bearing” is formed by the airflow § Slider acts like a racing car in “Ground Effect” § “Landing” in the data zone is a VERY BAD THING TO DO § “Head / Disk Interaction” (Head Crash) Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Magnetic Recording | March 2004 | © 2004 IBM

IBM Systems & Technology Group Magnetic Recording - schematic Soton. ac. uk 2004 |

IBM Systems & Technology Group Soton. ac. uk 2004 | Disk Drive Science |

IBM Systems & Technology Group Giant Magnetoresistive effect (GMR) ‘Pinned layer’ ‘Free layer’ More electron scattering Higher resistance R Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Giant Magnetoresistive effect (GMR) ‘Pinned layer’ ‘Free layer’ Less electron scattering Lower resistance R Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Disk Drive Evolution Soton. ac. uk 2004 | Disk

IBM Systems & Technology Group Where next? Soton. ac. uk 2004 | Disk Drive

IBM Systems & Technology Group Anti. Ferromagnetically Coupled media (“Pixie Dust”) Shrink domain size to drive up areal density, but… Demagnetisation energy ~ k. T 3 atom layer of Ru Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group Back to the Future – Punched cards? Soton. ac.

IBM Systems & Technology Group Millipede Soton. ac. uk 2004 | Disk Drive Science

IBM Systems & Technology Group A Parting shot – How safe is your data? § [Even IBM] Drives can fail – hence RAID § Density is also limited by error rates § Data is a tiny 400 MHz signal with S/N ratio close to 1 Soft error rates 1 in 106 bits § PRML data channel Partial Response – Maximum Likelihood (look for patterns) § Hard error rates: ‘Server class’ drives (SCSI or Fibre Channel) 1 in 1015 bits ‘Desktop class’ drives (ATA or S-ATA) 1 in 1014 bits § … 10% chance of a hard error in reading 1 TB for Desktop drives § Unacceptable for most commercial users – hence RAID Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation

IBM Systems & Technology Group The End “Thanks for Listening” | March 2004 |

IBM Systems & Technology Group Chemistry “What are all these parts made from? ”

IBM Systems & Technology Group Elements in a disk drive H Li Be Na. Mg Printed circuit board Electronics Magnets Mechanical Magnetic coating Electrical connections He B C N O F Ne Al Si P S Cl Ar K Ca Sc Ti V Cr. Mn. Fe Co Ni Cu. Zn. Ga. Ge. As Se Br Kr Rb Sr Y Zr Nb. Mo. Tc Ru. Rh Pd. Ag. Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au. Hg Tl Pb Bi Po At Rn Ce Pr Nd. Pm. Sm. Eu. Gd. Tb. Dy. Ho Er. Tm. Yb. Lu Soton. ac. uk 2004 | Disk Drive Science | © 2004 IBM Corporation