Lecture13nFull - COT 4600 Operating Systems Spring 2011...

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Click to edit Master subtitle style 8/1/11 Lecture 13 COT 4600 Operating Systems Spring 2011 Dan C. Marinescu Office: HEC 304 Office hours: Tu-Th 5:00 – 6:00 PM
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Lecture 13 8/1/11 n Last time: n Peer-to-peer systems n Remote Procedure Call n Strategies for name resolution n Case study: DNS – Domain Name Service ¨ Today n Case study: NFS – Network File System n Virtualization n Locks ¨ Next time n Review for the midterm Lecture 13 – Thursday, February 24, 2011 22
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Lecture 13 8/1/11 The Network File System n Developed at Sun Microsystems in early to early 1980s. n Application of the client-server paradigm. n Objectives: ¨ Design a shared file system to support collaborative work ¨ Simplify the management of a set of workstations n Facilitate the backups n Uniform, administrative policies n Main design goals 1. Compatibility with existing applications Y NFS should provide the same semantics as a local UNIX file system 2. Ease of deployment ” NFS implementation should be easily ported to existing systems 3. Broad scope “ NSF clients should be able to run under a variety of operating systems 4. Efficiency & the users of the systems should not notice a substantial performance degradation when accessing a remote file system relative to access to a local file system Lecture 12 33
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Lecture 13 8/1/11 NFS clients and servers n Should provide transparent access to remote file systems. n It mounts a remote file system in the local name space & it perform a function analogous to the MOUNT UNIX call. n The remote file system is specified as Host/Path ¨ Host the host name of the host where the remote file system is located ¨ Path 5 local path name on the remote host. n The NFS client sends to the NFS server an RPC with the file Path information and gets back from the server a file handle ¨ A 32 bit name that uniquely identifies the remote object. n The server encodes in the file handle: ¨ A file system identifier ¨ An inode number ¨ A generation number Lecture 12 44
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Lecture 13 8/1/11 55
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Lecture 13 8/1/11 Implementation n Vnode – a structure in volatile memory which abstracts if a file or directory is local or remote. A file system call ( Open, Read, Write, Close , etc.) is done through the vnode-layer. Example: ¨ To Open a file a client calls PATHNAME_TO_VNODE ¨ The file name is parsed and a LOOKUP is generated n if the directory is local and the file is found the local file system creates a vnode for the file n else ¨ the LOOKUP procedure implemented by the NFS client is invoked . The file handle of the directory and the path name are passed as arguments ¨ The NFS client invokes the LOOKUP remote procedure on the sever via an RPC ¨ The NFS server extracts the file system id and the inode number and then calls a LOOKUP in the vnode layer. ¨ The vnode layer on the server side does LOOKUP on the local file system
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This note was uploaded on 07/30/2011 for the course COP 4600 taught by Professor Montagne during the Spring '08 term at University of Central Florida.

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Lecture13nFull - COT 4600 Operating Systems Spring 2011...

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