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  • 1. Current Trends in Flash Memory Technology 2006. 01. 25 Sang Lyul Min Eyee Hyun Nam Seoul National University
  • 2. Agenda Overview of Portable Storage Technologies High Performance Flash Memory Controller Hybrid Hard Disk Drive Conclusions
  • 3. Portable Storage Applications Audio Handset Video PC
  • 4. The Contenders for Portable Storage Market Flash Drive Micro Drive IBM Hitachi Samsung Toshiba Hitachi Seagate Portable Storage SanDisk LexarMedia
  • 5. Cost Comparison (2004. 8) $399.95 (2004.8 $299.88 (2004.8) $259.88 (2004.8) Source: http://www.hitachigst.com/hdd/technolo/overview/chart03.html
  • 6. Cost Comparison (2005. 4) $214.99 (2005.4 $153.60 (2005.4) $78.99 (2005.4) Source: http://www.hitachigst.com/hdd/technolo/overview/chart03.html
  • 7. NAND Flash Memory Basics 2j blocks Data Spare Data Spare Data Spare Data Spare Data Spare Data Spare Data Spare Data Spare Data Spare 2i ……… pages … … … Data Spare Data Spare Data Spare Read physical page Erase block (chip #, block #, page #) (chip#, block #) ~ 25 us ~ 2 ms Write physical page (chip #, block #, page #) ~ 300 us
  • 8. FTL (Flash Translation Layer) Definition Software layer that makes flash memory appear to the system like a disk drive Challenges in FTL No overwrite is allowed without erasing Asymmetry in read and write speeds
  • 9. Logical interface for a disk drive 512B 512B … 512B 0 1 N -1 Operations 1. Identify drive(): returns N 2. Read sectors(start sector #, # of sectors) 3. Write sectors(start sector #, # of sectors)
  • 10. Block level mapping Logical blocks 0 1 N -1 Sectors … 256 sectors Logical … … … blocks 0 N / 256
  • 11. Block level mapping Logical to physical block mapping Logical blocks Visible (data blocks) Invisible … … … … … … 0 1 L Block mapping table (map block) … … … … Physical blocks
  • 12. Read procedure Ex. read 3 sectors from 255 Logical blocks … … … … … … 0 1 L Block mapping table (map block) … … … R R R … Physical blocks
  • 13. Write procedure (Data block update) Ex. write 3 sectors from 255 … … … … … … 0 1 L Block mapping table (map block) … … … … … W W W … … Write buffer blocks Still, update of write buffer blocks for data 1. Erase mapping information is needed 2. Write data pages pages 3. Fill remaining data
  • 14. Write procedure (Map block update) Ex. write 3 sectors from 255 … … … … … … 0 1 L Block mapping table (map block) … … … … … W W W … W … Write buffer blocks Still, somewhere we need to keep the addresses of 6. Erase and write buffer map for map Fill remaining map pages 5. Read-modify-writeblocks (i.e., logging) 4. new mapwrite buffer blockspage
  • 15. Inside Flash Drive CPU SRAM core System Bus Flash Bus Host Flash Interface Interface USB, PCMCIA, SATA Flash Chips
  • 16. Host Interface Performance Transfer Rate (MB/s) 800 SAS6Gbps 700 S-ATA3 600 500 IEEE SAS3Gbps 1394b 400 Ultra320 SCSI S-ATA2 300 IEEE 1394b 200 Ultra160 SCSI S-ATA1 IEEE IEEE 1394b 100 Ultra Ultra2 SCSI 1394a U-ATA66 2.0 USB SCSI-3 SCSI U-ATA33 SCSI-1 SCSI-2 ATA1 ATA2 USB 1.1 0 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 19 19 19 19 19 19 19 19 19 19 19 19 19 19 20 20 20 20 20 20 20 20 ATA SCSI SERIAL
  • 17. Flash Chip Bandwidth Write bandwidth = 2KB/300us = 6.7MB/s per chip Read bandwidth = 2KB/25us = 80MB/s per chip Erase bandwidth = 128KB/2ms = 64MB/s per chip
  • 18. Flash bus bandwidth picture 20~40Mb/s per Pin Flash Source: Terry Lee, Micron Technology, Inc, VTF (VIA Technology Forum) 2003
  • 19. Agenda Overview of Portable Storage Technologies High Performance Flash Memory Controller Hybrid Hard Disk Drive Conclusions
  • 20. Techniques for High Performance Flash Drive CPU SRAM core System Bus High speed Flash bus Flash Bus Host Flash Interface Interface USB, PCMCIA, etc “Sleeping with the enemy” “Getting out of the way” Flash Chips Multiple logical chips in a single packaging (multi-banking)
  • 21. Evaluation board from FAST group (Version 1 – Home-made)
  • 22. Evaluation board from FAST group (Version 2 with Samsung Electronics)
  • 23. PCMARK’04 HDD Benchmarks PCMARK’04 HDD Benchmark: a Storage System Benchmark Based on real usage Consists of Windows XP Startup Contains disk activities occurring at operating system start-up Application Loading Contains disk activities from loading (opening and closing) MS Word, Acrobat Reader, Windows Media Player, etc General Hard Disk Drive Usage Contains disk activities while executing MS Word, Winzip, Winamp, Internet Explorer, Picture Viewers, etc File Copying Contains disk activities from copying 400MB of files
  • 24. Performance Comparison (PCMark’04) HDD (2.5 in) Chameleon (FRAM 2Mbytes) Overall score 2499 8306 XP Startup 4.646 17.0 Application loading 3.670 15.4 File Copying 16.921 17.3 General HDD 3.045 11.4 Usage
  • 25. Why High Performance Flash Drive?
  • 26. A Critical Point in VLSI Technology Source: www.icknowledge.com
  • 27. A Critical Point in VLSI Technology and RISC Architecture Integration of processors on a single chip The critical point (“epoch”) Argued for different architectures (RISC) small repertoire of instructions in a uniform format Pipelined execution Cache memory Load/store architecture The rest is history Large/multi-level caches Co-processors Superscalar Speculation Simultaneous Multi-threading etc From “Single-Chip Multiprocessors: the Rebirth of Parallel Architecture” by Prof. Guri Sohi
  • 28. A Critical Point in Portable Storage
  • 29. Technical Impact of Large/High Performance Portable Storage: Stateless PC What’s inside mobile storage? 1 Virtual Machine Monitors 2. Operating systems 3. File systems 4. Preference profile 5. Digital DNA No Non-Volatile State (No Hard Disk, EEPROM, Flash) state Stateless PC
  • 30. Stateless Mobile Phone Analogy What’s inside sim card? 1 PIN number 2. Serial number 3. Encryption key 4. Network provider info 5. Phone book 6. Address book state Stateless GSM Mobile Phone
  • 31. Agenda Overview of Portable Storage Technologies High Performance Flash Memory Controller Hybrid Hard Disk Drive Conclusions
  • 32. Hybrid Hard Disk Drive HDD with reduced + = power consumption and start-up time HDD NAND Flash
  • 33. Why Hybrid Hard Disk Drive? 1. Power consumption aspects: In a laptop PC, HDD consumes ~10% (~2W) total power when disk platters are spinning ~1% (~0.2W) total power when disk platters are idle 2. Cost aspects: 128MB Flash write buffer < $8 in 2006 < $4 in 2008 3. Reliability aspects: 4. Performance aspects: Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004.
  • 34. Hybrid Hard Disk Drive Block Diagram CPU SRAM core System Bus Flash Bus Host Flash Interface Interface SATA Flash Chip Platters
  • 35. Key Benefits of Hybrid Hard Disk Drive 87% reduction in power can be achieved (1.75W) Assumptions Pavg active = ~2W (measured) Pavg with Flash write buffer and “Longhorn” kernel = 0.25W (calculated) Toff = 600s @ .18W Ton = 18s @ 2.5W Ton = spin up time (5s) + Flash buffer flush time (13s) Flash buffer size = 128MB Transfer rate = 10MB/s Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004.
  • 36. Key Considerations 1. Correctness: should preserve the semantics of HDD 2. Fault tolerance and graceful degradation: should operate correctly despite partial/total failure in flash memory 3. Power efficiency: should reduce the power consumption as much as possible 4. Reliability: should improve the reliability as much as possible 5. Performance: should improve the user-perceived performance as much as possible
  • 37. Agenda Overview of Portable Storage Technologies High Performance Flash Memory Controller Hybrid Hard Disk Drive Conclusions
  • 38. Conclusions In the animal world Survival of the fittest In the memory world Survival of the fastest or cheapest ? Volatile Non-volatile Fastest SRAM FRAM, PRAM, or MRAM? Cheapest DRAM NAND Flash HDD
  • 39. Conclusions From the history IBM 360/85 IBM 360/91 Clock Rate 80 ns 60 ns Memory Speed 1040 ns 750 ns Memory Interleaving 4 way 8 way Register Renaming, Additional Features Cache Memory Out-of-order Execution, etc But, IBM 360/85 faster on 8 of 11 programs! Source: David Patterson, et al., “A Case for Intelligent DRAM: IRAM”, Hot Chips VIII, August, 1996
  • 40. The Ultimate Limit – Micro Drive Fly 2,000,000 Miles Per Hour By Night Boeing 747 1/100” Flying Height Source: Richard Lary, The New Storage Landscape: Forces Source: shaping the storage economy, 2003. http://www.hitachigst.com
  • 41. The Ultimate Limit – Flash Drive B/L Direction 200nm W/L Direction Source: K. Kim et al. IEDM Tech. Dig., 2002, pp. 919-922