• Khoa học máy tính - Chapter 20: Distributed file systemsKhoa học máy tính - Chapter 20: Distributed file systems

    Transparency concerns association between path name of a file and location of the file File sharing semantics may differ between DFSs: Unix semantics Session semantics Transaction semantics (atomic transactions) Stateless server design provides high availability Notion of a hint used to improve performance DFS uses file caching to improve pe...

    ppt26 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 927 | Lượt tải: 0

  • Khoa học máy tính - Chapter 19: Recovery and fault toleranceKhoa học máy tính - Chapter 19: Recovery and fault tolerance

    Recovery from non-Byzantine faults can be performed by using two approaches: Backward recovery and forward recovery Fault tolerance implemented by maintaining logs E.g., undo or do logs Logs used to implement atomic transactions Two-phase commit protocol (2PC protocol) is used Nested transactions are a resiliency technique Used when transac...

    ppt22 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 919 | Lượt tải: 0

  • Khoa học máy tính - Chapter 18: Distributed control algorithmsKhoa học máy tính - Chapter 18: Distributed control algorithms

    Actions of a distributed control algorithms are performed in many nodes of the system Two aspects of correctness are liveness and safety Distributed system models: physical and logical Examples of distributed control algorithms: Distributed mutual exclusion: e.g., token based Distributed deadlock detection: diffusion computation Distributed s...

    ppt40 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 902 | Lượt tải: 0

  • Khoa học máy tính - Chapter 17: Theoretical issues in distributed systemsKhoa học máy tính - Chapter 17: Theoretical issues in distributed systems

    Using local clocks in processes Logical clocks Vector clocks Include process ids in timestamps for total ordering It is not possible to record the global state of a system Chandy-Lamport algorithm obtains consistent recording of process states using special messages called markers

    ppt28 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 902 | Lượt tải: 0

  • Khoa học máy tính - Chapter 15: Security and protectionKhoa học máy tính - Chapter 15: Security and protection

    Security and protection measures are used to counter interference threats Use authentication and authorization techniques Threats launched using Trojan horses, viruses, worms, and exploitation of buffer overflows Encryption is an algorithmic transformation of data Block ciphers and stream ciphers Widely used encryption standards: DES and AES ...

    ppt41 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 982 | Lượt tải: 0

  • Khoa học máy tính - Chapter 14: Implementations of file operationsKhoa học máy tính - Chapter 14: Implementations of file operations

    An access method improves the performance of a file processing activity within a process using buffering and blocking of records Caching reduces the number of I/O operations performed to access data stored in files Physical IOCS implements a disk cache An access method implements a file cache The virtual memory handler uses a page cache OSs us...

    ppt53 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 946 | Lượt tải: 0

  • Khoa học máy tính - Chapter 13: File systemsKhoa học máy tính - Chapter 13: File systems

    Files are structured or unstructured (byte stream) File system provides: File organizations (sequential, direct, indexed) Directories for grouping of related files logically Sharing and protection of files Disk space allocation, typically indexed File map table (FMT) stores allocation information File control block (FCB) stores information a...

    ppt65 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 883 | Lượt tải: 0

  • Khoa học máy tính - Chapter 12: Virtual memoryKhoa học máy tính - Chapter 12: Virtual memory

    Which page should VM manager remove from memory to make space for a new page? Page replacement algorithms exploit locality of reference LRU has stack property, but is expensive NRU algorithms are used in practice E.g., clock algorithms How much memory should manager allocate? Use working set model to avoid thrashing Copy-on-write can be used...

    ppt57 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 963 | Lượt tải: 0

  • Khoa học máy tính - Chapter 11: Memory managementKhoa học máy tính - Chapter 11: Memory management

    Allocation/deallocation of memory can lead to fragmentation: internal or external First-fit, next-fit and best-fit strategies try to reduce fragmentation buddy systems and power-of-2 allocators eliminate external fragmentation Noncontiguous allocation reduces external fragmentation Requires use of the memory management unit (MMU) of CPU Kernel...

    ppt50 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 848 | Lượt tải: 0

  • Khoa học máy tính - Chapter 10: Synchronization and scheduling in multiprocessor operating systemsKhoa học máy tính - Chapter 10: Synchronization and scheduling in multiprocessor operating systems

    Multiprocessor OS algorithms must be scalable Use of special kinds of locks: Spin locks and sleep locks Important scheduling concepts in multiprocessor OSs: Affinity scheduling Coscheduling Process shuffling

    ppt30 trang | Chia sẻ: nguyenlam99 | Ngày: 10/01/2019 | Lượt xem: 789 | Lượt tải: 0