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  • 1. 전체적으로 대 / 소 문자 통일
  • 내려오는 flow 를 animation 으로 날리고 , text 역시 animation 으로 가장 나중에 등장하도록
  • F 는 의 한계점 하고 , Applicaion 의 random 으로 인한것 만 고려 두개만 남기고 .. 둘은 날릴것 .
  • 실제 호환성을 위해 block device interface 를 유지 해야 하기 때문에 , 블록 단위 meta
  • 보드 언급은 하지 말고 ~~ ^^ 32, 16KB 가 가장 많이 사용하는 buffer size 라는 것을 표기 하는 animation 및 박스 표기 추가 하고 , 평균 성능 향상 percent 표기
  • 박스 집어 넣어서 .. 강조 하고 . 시간에 따라 시간이 부족 할 경우 ,  간략하게 이유만 설명 하는 방향으로
  • PRAM 영역은 NOR 대체 기 때문에 , Code 저장하고 , 남은 공간을 사용하기 때문에 .. 공짜다 .. 강조 System 구현 cost 는 늘지 않는다 . ^^
  • Biz Impact 에 대한 언급 … Summary 후에 . FeRAM 은 언급 빼고 .. Future work 외에 business impact 에 대한 언급을 더 하자 .
  • 예상 질문 리스트 만들고 .. 참고 appendix ppt 준비 할 것 . 이철 책임님 : PRAM 관리 코드 overhead  답 FSMS

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  • A PRAM and NAND Flash Hybrid Architecture for High-Performance Embedded Storage Subsystems Jin Kyu Kim, Samsung Electronics Hyung Gyu Lee, Samsung Electronics Shinho Choi, Samsung Electronics Kyoung Il Bahng, Samsung Electronics
  • Why Hybrid Approach ? ≤
    • Gasoline Engine
    • - Gasoline price is high
    • - Pollution
    • - Fuel Efficiency depends on traffic
      • [+]Good for high way
      • [-]Bad for heavy traffic
    • [+] Fuel capacity is large
    Electronic Motor [+] Electricity price is reasonable [+] No pollution [+] Good fuel efficiency [-] Fuel capacity is very limited
  • Era of Hybrid Approach
    • NAND Flash
    • [-] Short life span
    • [-] W Performance depends on access
      • [+]Good for large sequential access
      • [-]Bad for small random access
    • [-] No support for byte access
    • [+] Very high density
    NVRAM [+] Long life span [+] Good performance [+] Support for byte access [-] Low density NAND Flash NVRAM User Data Meta Data
  • Characteristics of NVRAM(PRAM)
    • Flash memory device
      • Erase before program
      • Different granularity on erase and program operations
      • Limited life time
      • High Density (NAND)
    • NVRAM
      • Fast read/write
      • Byte operation (random access)
      • No erase operation
      • Capacity (cost) problem
  • Memory Components
  • Overall Storage Hierarchy Performance Problems !
      • User data (Clusters)
      • Large size data
      • Sequential access pattern
      • SectorUnit I/O ⇒ Appropriate for NAND property
      • Meta data (Clusters)
      • Small Size Data
      • Frequently updated
        • ⇒ Appropriate for PRAM property
      • Mixed Pattern  Random Pattern
      • Main reason for FTL performance degradation
      • Performance degradation for overall storage
  • Motivations
    • In Filesystem Level
    • In addition to user data, file system needs to manage meta data
    • The properties of meta data degrade FTL performance
      • degrade the throughput of file system
    • If store FS metadata into NVRAM instead of NAND
    • Decrease overhead for handling Metadata I/O
    • Decrease random access I/O to FTL
    Motivation 1
    • In FTL Level
    • Performance and Performance stability depends on the mapping algorithm
    • FTL performance depends on user(Filesystem) 의 Access Pattern
    Page Mapping - High performance - High resource consumption Block Mapping - Low performance - Low resource consumption Mapping granularity Fine granularity Coarse granularity High performance Low performance Degree of random access Low High If implement FTL with NVRAM  Page Mapping without large amount of memory memory  Stable against random access through fine granularity Motivation 2
  • Motivations
    • In Filesystem Level
    • In addition to user data, file system needs to manage meta data
    • The properties of meta data degrade FTL performance
      • degrade the throughput of file system
    • If store FS metadata into NVRAM instead of NAND
    • Decrease overhead for handling Metadata I/O
    • Decrease random access I/O to FTL
    Motivation 1
    • In FTL Level
    • Performance and Performance stability depends on the mapping algorithm
    Motivation 2 Coarse grained mapping FTL Fine grained mapping FTL Fine grained mapping FTL with NVRAM Resource Performance
  • Overall Scheme – FSMS, hFTL
  • Approach in File System Level FSMS (File System Metadata Separation)
  • File System Metadata Separation Scheme
    • Separate File System Meta data [FAT,DIR,Log] from NAND Flash
      • Store FS Metadata on PRAM  Decrease random access to FTL
      • Only the user data will be stored on NAND flash
      • Random Access decrement -> FTL overhead decrease -> Performance and life span of NAND flash increase
  • Approach in Block Device Level hFTL (PRAM+NAND hybrid storage FTL)
  • Need for hFTL
  • Implementation of hybrid FTL
  • Implementation of hybrid FTL
    • PRAM, NAND Layout
  • Performance Optimizations - 1
    • Filtering between FS and PRAM device
    • On the average, only 16 % of one metadata block is changed
  • Performance Optimizations-2
    • Functionality of Logical Delete
    Remove management Overhead of the space occupied by deleted file
  • Evaluations
    • Evaluation Setting
      • S3C2413 CPU board
        • 1 Channel, 1 NAND device support
        • (MLC and SLC)
      • 64MB PRAM (KPS1215EZM)
      • 1GB MLC NAND (K9G8G08U0M)
    • Evaluations
      • Comparison Target: log block FTL
      • Criterion
        • Performance
          • LLD Layer (Low Level Device driver)
          • FTL Layer (Block Device driver)
          • File system Layer (TFS4)
        • Life span: Erase count
        • Cost : code and data size
    PRAM NAND
  • LLD, FTL-Level Evaluation
    • LLD (Low Level Device driver)
      • Read: 4.25MB/s, Write 1.7MB/s
    • FTL
      • Sequential Read: 4.16MB/s (LB-FTL, hFTL Similar)
      • Random Read: 4.09MB/s (LB-FTL, hFTL Similar)
      • Sequential Write: 1.62MB/s (LB-FTL, hFTL Similar)
      • Random Write :
  • File System Level Evaluations
    • IOzone benchmark for Sequential I/O
  • File System Level Evaluations
    • IOzone benchmark for Random I/O
  • Life Span and Implementation Cost
    • Life Span
    • Implementation Cost
    Required PRAM for 1GB NAND: For FSMS : 2 MB For hFTL : 2.5 MB
  • Contribution
    • Summary
      • Suggest SW scheme for efficient usage of NAND/PRAM Hybrid Storage
        • FSMS
        • hFTL
      • Enhance the performance compared to NAND only storage
        • FSMS, hFTL take effects orthogonally
        • For, sequential write, the effects of FSMS is larger than that of hFTL
        • For, random write, the effects of hFTL is larger than that of F 는
        • hFTL+FSMS shows better performance than LBFTL by up to 290%.
        • hFTL shows better performance than LBFTL+FSMS.
    • Future work
      • Aggressive optimization using NGNVMs in File System Level
      • Scalability for large NAND flash storage
  • NAND v.s. PRAM In current technology, it’s hard to replace NAND flash with PRAM device. However, it’s enough to replace NOR flash Page Access Need for Erase 10 4 1.4ms 800us(page) 60us(page) Serial access:30ns NAND(MLC) 1.4ms N/A Block Erase Time 200us(page) 10us (word) Word Program Time Page Access Need for Erase Byte Access No need for Erase Features 10 5 10 6 Life span 20us(page) Serial access:25ns Async: 80ns Sync: 10ns Access time NAND(SLC) PRAM Features