3. distributed file system requirements
-
Upload
abdul-thayyal -
Category
Documents
-
view
89 -
download
1
Transcript of 3. distributed file system requirements
![Page 1: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/1.jpg)
DISTRIBUTED FILE SYSTEMS(DFS)
![Page 2: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/2.jpg)
DISTRIBUTED FILE SYSTEMS
• Including1.Introduction2.File Service Architecture3.Case Study: Sun NFS
![Page 3: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/3.jpg)
1. Introduction
• File system: support convenient programming interface to disk storage, access control and file looking mechanism.
![Page 4: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/4.jpg)
Distributed File Systems CS-4513, D-Term 2007 4
Distributed Files Systems (DFS)
• Allows multi-computer systems to share files & Sharing devices
• E.g.,– NFS (Sun’s Network File System)– Windows NT, 2000– Andrew File System (AFS)
![Page 5: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/5.jpg)
Distributed File Systems CS-4513, D-Term 2007 5
Distributed File Systems (continued)
• One of most common uses of distributed file system is distributed computing
• Goal: provide common view of centralized file system, but distributed implementation.– Ability to open & update any file on any machine
on network– All of synchronization issues and capabilities of
shared local files
![Page 6: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/6.jpg)
Including
1. Characteristics of file system
2. Distributed File system requirements
![Page 7: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/7.jpg)
1. Characteristics of file system
• File system: support convenient programming interface to disk storage, access control and file looking mechanism.
Files contain both data and attributes.
A typical attribute record structure is illustrated in Figure 3.
![Page 8: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/8.jpg)
8
IntroductionFile length
Creation timestampRead timestampWrite timestamp
Attribute timestampReference count
OwnerFile type
Access control list
Figure 3. File attribute record structure
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005
![Page 9: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/9.jpg)
• Figure 4 summarizes the main operations on files that are available to applications in UNIX systems.
![Page 10: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/10.jpg)
10
Introduction
filedes = open(name, mode)filedes = creat(name, mode)
Opens an existing file with the given name. Creates a new file with the given name. Both operations deliver a file descriptor referencing the openfile. The mode is read, write or both.
status = close(filedes) Closes the open file filedes.
count = read(filedes, buffer, n)
count = write(filedes, buffer, n)
Transfers n bytes from the file referenced by filedes to buffer. Transfers n bytes to the file referenced by filedes from buffer.Both operations deliver the number of bytes actually transferredand advance the read-write pointer.
pos = lseek(filedes, offset, whence)
Moves the read-write pointer to offset (relative or absolute,depending on whence).
status = unlink(name) Removes the file name from the directory structure. If the filehas no other names, it is deleted.
status = link(name1, name2) Adds a new name (name2) for a file (name1).
status = stat(name, buffer) Gets the file attributes for file name into buffer.
Figure 4. UNIX file system operations
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005
![Page 11: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/11.jpg)
11
2. Distributed File system requirements
Related requirements in distributed file systems are:
1. Transparency2. Concurrent file updates3. File Replication4. Hardware & Operating system Heterogeneity5. Fault tolerance6. Consistency7. Security8. Efficiency
Couloris,Dollimore and Kindberg Distributed Systems: Concepts & Design Edn. 4 , Pearson Education 2005
![Page 12: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/12.jpg)
1. Transparency
• Transparency defined as the concealment from the user and application programmer of the separation of components in a distributed system.
• Client programs should be unaware of the distribution of files.
![Page 13: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/13.jpg)
1. Transparency
1. Access transparency
2. Location transparency
3. Mobility transparency
4. Performance transparency
5. Scaling transparency
![Page 14: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/14.jpg)
1. Access transparency
• enable local & remote file to be accessed using identical operations.
![Page 15: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/15.jpg)
2. Location transparency
enables files to be accessed without knowledge of their physical or network location.
![Page 16: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/16.jpg)
3. Mobility transparency
• Allows the movement of files within a system without affecting the operation of users or programs.
![Page 17: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/17.jpg)
4. Performance transparency
• Allows the system to be reconfigured to improve the performance as loads vary.
![Page 18: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/18.jpg)
5. Scaling transparency
• Allows the service can be expanded.• increase in size of storage and network size
should be transparent.
![Page 19: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/19.jpg)
2. Concurrent file updates
• Concurrent file updates is protected by locking.
• Simultaneously accessing or changing the same file.
![Page 20: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/20.jpg)
3. File Replication
• File service maintains multiple identical copies of files.
• Load sharing between server makes service more scalable.
![Page 21: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/21.jpg)
4. Hardware & Operating System Heterogeneity
• Service can be accessed by clients running on any OS or any hardware platform.
![Page 22: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/22.jpg)
5. Fault Tolerance
• If the service is replicated, it can continue to operate even during a server crash.
![Page 23: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/23.jpg)
6. Consistency
• Unix offers one –copy update semantics for operation on local files.
• Difficult to achieve the same for distributed file systems.
![Page 24: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/24.jpg)
7. Security
• Must maintain access control and privacy as for local files.
• Digital signatures and encryption for secret data.
![Page 25: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/25.jpg)
8. Efficiency
• Goal for distributed file system is usually performance comparable to local file system.
![Page 26: 3. distributed file system requirements](https://reader034.fdocuments.us/reader034/viewer/2022042602/55a4e4be1a28ab2b748b468e/html5/thumbnails/26.jpg)
Thank You