21.DistributedFileSystems

21.DistributedFileSystems - FileSystems Withcontentfrom...

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1 Network and Distributed File Systems With content from Distributed Communication Systems Christophe Bisciglia, Aaron Kimball, & Sierra Michels-Slettvet
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2 From Local to Network File System So far, we have assumed that files are stored on local disk … How can we generalize the design to access files stored on a remote server? Need to invoke file creation and management methods on the remote server Basic mechanisms: Message passing primitives Remote Procedure Calls (RPC)
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3 A network file system is likely to be better than a local file system in what respects? A. Read/write performance B. Availability C. Fault tolerance D. Ease of management
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4 Communication and synchronization based on. .. Shared memory Assume processes/threads can read & write a set of shared memory locations Inter-process communication is implicit, synchronization is explicit Process Coordination Two fundamental approaches thread thread Execution Stack Execution Stack Program Code Program Code Data Data Execution Stack Execution Stack receive ( message ) process process send ( message ) Message passing Inter-process communication is explicit, synchronization is implicit
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5 Process Coordination Shared Memory v . Message Passing Shared memory Efficient, familiar Difficult to provide across machine boundaries.     send(int id, String message); receive(int id, String message);      send(int  id,  String  message ); receive(int  id,  String  message ); Canonical syntax: process foo begin     :   x := 1    : end foo process bar begin     :   while(x==0) ;    : end bar global     int x = 0; Message passing Extensible to communication in distributed systems
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6 Message Passing Naming communicants How do processes refer to each other? Does a sender explicitly name a receiver? Can a receiver receive from a group? (a reduction operation) “Mailbox” “Mailbox” S R 1 R 2 R m . “Port” “Port” R S 1 S 2 S n S R Can a message be sent to a group?
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7 Web requests conform to what model? 1. Many-to-one 2. One-to-one 3. One-to-many
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8 Message Passing Issues Synchronization semantics When does a send / receive operation terminate? OS Kernel Sender Receiver OS Kernel Sender Receiver Partially blocking/non-blocking: send() / receive() with  timeout Non-blocking:  Send operation “immediately” returns Receive operation returns if no message is available Blocking: Sender waits until its message is received Receiver waits if no message is available
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9 Semantics of Message Passing send ( receiver , message ) Send message to receiver Wait until message is accepted.
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This document was uploaded on 03/09/2012.

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21.DistributedFileSystems - FileSystems Withcontentfrom...

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