Advanced Information Storage 05

Transcription

1 Advanced Information Storage 05 Atsufumi Hirohata Department of Electronics 15:00 21/October/2013 Monday (P/L 005) Quick Review over the Last Lecture Logical conjunctions : Notations : Venn diagrams : Logic circuits : AND OR A (Ā) A B A B NOT A B NAND NOR A B A B A B XOR A B A B A B A Ā A B

2 05 Magnetic Tape Storage 1 Advantages Development Linear recording Helical recording 1 / 2 reel Linear tape open Access Patterns to a Hard Disk Drive Research on access patterns on network attached storages (NAS) : * *

3 Information storage is required : * Origins of Data Loss * Why Tape Storage? Magnetic tape media : * -times-more data are stored as compared with a hard disk drives (HDD). Almost EB data are stored in tape media Almost tapes! Tapes

4 Data Transfer Speed Magnetic tape media : * Without compression, MB / sec. ( GB / h). Almost comparable with a HDD HDD Tapes Optical disks Where are Magnetic Storages Used? World-wide enterprise disk storage consumption : *

5 Energy Consumption Energy costs : * Tape media : LTO-5 without compression Initial 3 PB data + 45 % annual increase for 12 years Total cost of ownership (TCO) : 1/ of HDD Energy cost : 1/ of HDD Multi-tiered storage can be economical : * Economics of Modern Storage *

6 First Magnetic Tape Drive In 1951, Remington Rand introduced the first tape drive for a computer : * UNIVAC (Universal automatic computer) I uses a tape drive, UNISERVO. ½-inch wide tape Nickel-plated phosphor bronze (Vicalloy) 1,200 feet long 8 channels ( for data, for parity and for timing) inch / sec. (= characters / sec.) * IBM 7 Tracks In 1952, IBM also introduced a magnetic tape storage : * ½-inch wide tape 1,400 feet long 7 channels ( for data and for parity) inch / sec. (= characters / sec.) 6-bit characters In 1964, IBM introduced a 9 tracks : * ½-inch wide tape 2,400 feet long 9 channels ( for data and for parity) inch / sec. ( kb / sec.) 8-bit characters *

7 Linear Recording Method Linear recording : Data in long parallel tracks up to the tape length Multiple heads simultaneously write / read Very configuration Very data density * Linear Serpentine Recording In 1984, DEC introduced Digital Linear Tape (DLT) : * ½-inch wide tape Compac Tape I cartridge kb / sec. *

8 Helical Scan Recording In 1956, Toshiba developed the first helical scan recording for a video tape recorder : * Tilt read / write head (drum) -density recording * * Advanced Intelligent Tape In 1996, Sony introduced Advanced Intelligent Tape (AIT) : * 8-mm wide tape 25 ~ 800 GB (without compression) MB / sec. (without compression) Memory in cassette (MIC) : 64-kbit Electrically erasable programmable read-only memory (EEPROM) stores usage history and data address. Fast operation Adaptive lossless data compression (ALDC) : Data compression ~ 1/2.6. High recording density *

9 Digital Data Storage In 1987, Sony introduced Digital Audio Tape (DAT) : * Digital Data Storage (DDS) was then developed in inch (3.81-mm) or 8-mm wide tape 60 ~ 170 m long 2 write heads at 6 angle with 9,000 rpm ~ mm / sec. ( MB / sec.) > 17M units shipped ~ 50 % in magnetic tape storage Mode motor Head cleaner Head cleaner (under the plate) Head Head Capstan roller Guiding roller Cassette cartridge * 2 read / write heads : * Minimisation of Bit Errors Two adjacent tracks with their azimuth angle at ± 20 *

10 2 pairs of read / write heads : * Head Configuration Write head Read head Metal-in-gap layer Glass Non-magnetic ceramics Gap length Magnetic ferrite core Magnetic lamination Data track width (DAT 72 = 5.4 µm) * Capacity doubles every 3 year : * Development of a DDS *

11 Tape Cartridges One reel : * Tape is loaded into the system. Two reels : * Tape is loaded into the system. Head Tape is not loaded into the system. Exposed to a head * Linear Tape Open In 2000, IBM, HP and Seagate introduced Linear Tape Open (LTO) : * Based on research at IBM Tucson Laboratory DLT and AIT have dominated the market. Accelis : 8-mm wide tape 2 reels High access speed Resembles Sony AIT Ultrium : ½-inch wide tape 1 reels and linear scan Large storage capacity Resembles Quantum DLT 100 GB capacity (without compression) MB / sec. *

12 LTO Ultrium Roadmap * High Fidelity Operation Read-while-write : * Written data is checked by reading out the data immediately after writing. Head module Tape motion direction Tape Written data Tracks Write head Read head

13 Rewrite Operation In case the read-while-write operation found an error : * Data is rewritten until the error disappears. Tape motion direction Tape Rewritten data Written data with an error Tracks Write head Read head Rewrite until the error disappears. Data Distribution Operation Data subsets are repeatedly stored in various tracks : * Minimises a risk of data loss. Data subset 0 Error across tracks Track 1 Track 2 Track 3 Track 4 Track 5 Track 6 Track 7 Track 8 Error along a track

14 Precise Positioning Data subsets are repeatedly stored in various tracks : * Surface smoothness Data track 1280 Tape width ~ 1.27 cm 20 μm Sapporo Tape length ~ 800 m Distribution in left / right Kagoshima LTO Tape Media Track width of LTO tape media : * mm wide tape / Track width : tracks µm Top ferromagnetic layer Bottom non-magnetic layer Smooth base film (PET, PEN or PA) 70 ~ 80 % thickness Back coating Servo-signal Servo-band Track width : 8.1 µm