The Challenges of Magnetic Recording on Tape for Terabyte Capacities

Transcription

1 The Challenges of Magnetic Recording on Tape for Terabyte Capacities Richard H. Dee Storage Technology Corporation 1 StorageTek Drive, Louisville, Colorado Phone: FAX: richard_dee@storagetek.com Presented at the THIC Meeting at the National Center for Atmospheric Research Boulder CO June 11-12, 2002

2 Capacity and Data Rates Capacity = NbLε 8 DataRate = nbvε 8 N = number of tracks, b = bit density, L = length of tape, ε = efficiency, n =number of channels, V = tape speed

3 Capacity and Data Rates (alt.) Capacity = ( tpi)( bpi) 8 WLε DataRate = n ( bpi) 8 Vε tpi = track density, bpi = bit density, L = length of tape, W = width of tape, ε = efficiency, n =number of channels, V = tape speed

4 TeraByte Operating Points ½"wide tape, 3480/9940 form factor Capacity (TB) Data Rate (MB/sec) No. of Pll Data Channels, n No. of Data Tracks, N Trk. Pitch (µm) Channel Pitch, c p (µm) Rd. Track Width (µm) Tape Speed, V (m/s) Bit Density (kbpi) Track Density (tpi) Areal Density (Gb/in 2 ) Bit Cell (nm) Bit Cell (ns) Write Eq. Pulse (ns) Tape Length (m) Write Time per Cart. (min)

5 Block Diagram of a Magnetic Recording Channel

6 Digital Magnetic Recording

7 Linear Density Trend 300 kbpi MPX/Metal 2700 MP (Oe)? MP (Oe) MP (Oe) 50 0 Fe 2 O (Oe) CrO (O ) Year trends.xls

8 Recording Theory Transition from +M r to M r over a distance, a a ArcTangent Transition M(x) (emu/cc) x (nm) a ( ) = 2M π tan r 1 M x x a 2 M rδ δ = d H c recording.xls All these parameters are scaling down

9 Tape Media Section Diagram Backcoat Substrate δ Underlayer Magnetic Layer

10 Particulate Tape Media Progression

11 Recording Theory Transition from +M r to M r over a distance, a a ArcTangent Transition M(x) (emu/cc) x (nm) a ( ) = 2M π tan r 1 M x x a 2 M rδ δ = d H c recording.xls All these parameters are scaling down

12 Recording Theory (2) Spacing Loss due to Head-Medium spacing, d d Loss = 55 λ Signal to Noise Ratio depends on the number of particles being read 2 nwλ SNR = 6

13 Areal Density Limit Calculation A lim = t psnr t = track density, p = particle density, SNR = Signal-to-Noise Ratio The Foundations of Magnetic Recording, J. C. Mallinson, (Second Ed.), Academic Press (1993).

14 Areal Density Limit Calculation (Gbit/sq.in) (2) (8000 tpi) SNR(dB) Particle Density, p (cm -3 )

15 TeraByte Operating Points ½"wide tape, 3480/9940 form factor Capacity (TB) Data Rate (MB/sec) No. of Pll Data Channels, n No. of Data Tracks, N Trk. Pitch (µm) Channel Pitch, c p (µm) Rd. Track Width (µm) Tape Speed, V (m/s) Bit Density (kbpi) Track Density (tpi) Areal Density (Gb/in 2 ) Bit Cell (nm) Bit Cell (ns) Write Eq. Pulse (ns) Tape Length (m) Write Time per Cart. (min)

16 Head Technology

17 Thin Film Write Head Array

18 Media Stability Consequences D = 2 ( OT ) LWVb 64 Cc p m c 2 ε 2 OT Offtrack allowance c p channel pitch m c media stability coeff.

19 Data Rate Capacity Trade Off Data Rate/Capacity Tradeoff (10m/s, CP=50µm, 200kbpi, 12mm tape, 10% OT) Media Instability 700 Data Rate (MB/s) ppm 500pm 1000ppm 32 NSIC Capacity (TB) / 1000m of tape Ntracks.xls 16 8

20 TeraByte Operating Points ½"wide tape, 3480/9940 form factor Capacity (TB) Data Rate (MB/sec) No. of Pll Data Channels, n No. of Data Tracks, N Trk. Pitch (µm) Channel Pitch, c p (µm) Rd. Track Width (µm) Tape Speed, V (m/s) Bit Density (kbpi) Track Density (tpi) Areal Density (Gb/in 2 ) Bit Cell (nm) Bit Cell (ns) Write Eq. Pulse (ns) Tape Length (m) Write Time per Cart. (min)

21 Media Coercivity Time Dependence Figure 6. Coercivity of MP tape versus time scale of the applied magnetic field.

22 Magnetic Recording with Short Pulses (MP Tape) Normalized Output Output Efficiency Efficiency* Iw vs pulse.xls Pulse Length (ns)

23 Areal Density Trends Gb/in SONY Demos NSIC Roadmaps 1998 (Thin Film Media/ GMR Heads) 2001 MP Limit? MP Media / FullThin Film Heads Oxide Media / Ferrite Based Year trends.xls

24 Summary Medium has primary impact on areal density growth M r δ has to be reduced (as it was in disk) Side-by-side head channel architecture sets up tradeoffs Head technology in good shape (StorageTek Tour)! Limit for MP tape ~10Gb/in 2 (Careful!! Disk prediction in Gb/in 2 ) Tape wins on volumetric efficiency and $/GByte Tape not near any fundamental limits at this time