© 2004 IBM Corporation IBM Systems & Technology Group | March 2004 | Disk Drive Science IBM Systems & Technology Group Steve P Legg IBM SSG Hursley
Jan 11, 2016
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Disk Drive Science
IBM Systems & Technology GroupSteve P LeggIBM SSG Hursley
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
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?
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
…Grandmothers
Data capacity ~ 100MB ? Data rate ~ 10b/s Error rate ? Reliability ? Manufacturing cost ? Maintenance cost ?
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Agenda
Demand for disk storage What drives areal density?
Aerodynamics
Magnetic recording Future storage technologies
N S
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Magnetic disk vs. DRAM
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Disk Capacity Demand
Who needs all this stuff anyway?
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
CERN LHC
50 yrs, pure research, technology (NMR, PET, X-ray imaging, WWW)
27km tunnel, 100m below FR/CH 14TeV hadron collider
Scheduled start April 2007
Storage requirements:109 events / sec 1PB/s raw data rate
Hardware filtering to 100MB/s 1PB/yr
By 2008, 15PB/yr
Generate approx 1% of world data production
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Disk drive capacity - definitions
B Byte = One letter or number “A” KB Kilobyte = 1000 B (~ few line e-mail) MB Megabyte = 1000 KB (~ Bible or Qu’ran) GB Gigabyte = 1000 MB (~ human
genome) TB Terabyte = 1000 GB (~ Books,
annually) PB Petabyte = 1000 TB (Large companies) EB Exabyte = 1000 PB (Human
knowledge) ZB Zettabyte = 1000 EB 1021B YB Yottabyte = 1000 ZB 1024B
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Driving Areal density
5 decades of refinement
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Inside the head-disk enclosure
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Disk Drive Basics Performance: “seek”, “rotational latency”
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Aerodynamics
“Cruising at an altitude of 0.000001 feet”
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Actuator Assembly - close up
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Head / Disk interface
Disk Substrate (Aluminium or Glass)
Disk Coating (NiCrMo alloy + 3 atoms Ru)
Slider (Ferrite, Fe/Silicate glass)Head
Tiny air gap!~0.0000000200m (200nm)
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Evolution of flying height
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
The Slider
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Managing flying height
Demo (if it works)
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Disk Surface Preparation
Head / SliderFull Surface Texture
Zone Texture
No TextureRamp or lift mechanism
Dedicatedlanding zone Smooth
data zone
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
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)
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Magnetic Recording
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Magnetic Recording - schematic
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Giant Magnetoresistive effect (GMR)
‘Pinned layer’ ‘Free layer’
R
More electron scatteringHigher resistance
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Giant Magnetoresistive effect (GMR)
‘Pinned layer’ ‘Free layer’
R
Less electron scatteringLower resistance
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Disk Drive Evolution
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Where next?
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
AntiFerromagnetically Coupled media (“Pixie Dust”)
Demagnetisation energy ~ kT3 atom layer of Ru
Shrink domain size to drive up areal density, but…
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Back to the Future – Punched cards?
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Millipede
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
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 400MHz 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 1TB for Desktop drives
Unacceptable for most commercial users – hence RAID
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
The End
“Thanks for Listening”
© 2004 IBM Corporation
IBM Systems & Technology Group
| March 2004 |
Chemistry
“What are all these parts made from?”
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
Elements in a disk drive
Cs Ba La Hf Ta W ReOs Ir Pt AuHg Tl Pb Bi Po At Rn
Rb Sr Y Zr NbMoTcRuRhPdAgCd In Sn Sb Te I Xe
K Ca Sc Ti V CrMnFe Co Ni CuZnGaGeAs Se Br Kr
NaMg
Li Be
H
Al PSi S Cl Ar
B C N O F Ne
He
Ce Pr NdPmSmEuGdTbDyHo ErTmYbLu
Printed circuit boardElectronicsMagnetsMechanicalMagnetic coatingElectrical connections
Si
O
Si
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation
IBM Systems & Technology Group
Soton.ac.uk 2004 | Disk Drive Science | © 2004 IBM Corporation