MECH 2301 Lecture Notes - Lecture 32: Indexed File, Ntfs, Inode
22 May 2018
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MECH 2301 Lecture 32 Notes
Introduction
Windows NTFS file system
• As you will see the file management system maintains a directory structure that
identifies and locates each file by name.
• Directory entries also store the attributes of the file that we mentioned earlier.
• Some systems store a single pointer to the index block in the directory entry as a way of
locating the file.
• Other systems store link pointers in the directory entry itself.
• The following examples show two of the most common approaches, the UNIX i-node
method and the NTFS method.
• UNIX and Linux use an indexed file allocation method
• The directory entries in a UNIX system each contain just the name of the file plus a
single pointer to an index block called an i-node.
• The i-node for a file contains the index pointers, and also the attributes of the file.
• A typical i-node design allocates thirteen index pointers.
• The first ten pointers are links, just as we have described.
• This is adequate for small files.
• In fact, the needs of most of the files on the system are met this way.
• The last three entries in the table serve a special purpose.
• These are called the single indirect, double indirect, and triple indirect block pointers.
• The single indirect block pointer points to another index block.
• Additional links are found in that block.
• The number of links is determined solely by the size of a standard disk block.
• The double and triple indirect blocks are two and three steps removed, respectively.
• We have shown the single and double indirect blocks on the diagram.
• Using 4 KB clusters, this scheme is sufficient to access files in the hundreds of gigabytes.
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