Questions and Answers
What are the three kinds of files in a file structure?
The three kinds of files in a file structure are byte sequence, record sequence, and tree.
What is the main difference between sequential access and random access in file systems?
Sequential access involves reading all bytes/records from the beginning, whereas random access allows reading bytes/records in any order.
What is an executable file in the context of file types?
An executable file is a file that contains machine code that can be executed directly by the computer.
What is the purpose of the 'seek' file operation?
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What are file attributes, and why are they important?
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What is the difference between a file's 'get attributes' and 'set attributes' operations?
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What is the primary benefit of using memory-mapped files?
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In a single-level directory system, how are files organized?
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What is the purpose of the readdir operation in a directory system?
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How do hierarchical directory systems organize files and directories?
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What is the main difference between a single-level and a two-level directory system?
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What is the purpose of a path name in a file system?
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What is the main difference between contiguous allocation and linked allocation of disk space?
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What is the purpose of an i-node?
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How are long file names handled in directories?
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What is the benefit of using a file allocation table (FAT) in RAM?
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What is the purpose of quotas in disk space management?
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What is the strategy used by log-structured file systems?
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How do file systems handle shared files?
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What is the purpose of a block cache in file system performance?
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What is the difference between a file system's logical and physical structure?
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What is the advantage of using a bit map for disk space management?
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Study Notes
File Systems and Disk Management
- Long-term information storage must store large amounts of data, survive process termination, and allow multiple processes to access information concurrently.
File Naming
- Files have typical extensions.
File Structure
- There are three kinds of files: byte sequence, record sequence, and tree.
File Types
- There are various file types, including executable files and archives.
File Access
- Sequential access reads all bytes/records from the beginning and cannot jump around, convenient for magnetic tapes.
- Random access reads bytes/records in any order, essential for database systems.
File Attributes
- Files have possible attributes.
File Operations
- File operations include create, delete, open, close, read, unlink, append, seek, get attributes, set attributes, and rename.
File System Implementation
- A possible file system layout consists of a file allocation table, inode table, and data blocks.
- Contiguous allocation of disk space can lead to fragmentation.
- Linked list allocation uses a file allocation table in RAM.
- Inode allocation uses a file allocation table in RAM and a disk block pointer.
Implementing Directories
- A simple directory has fixed-size entries with disk addresses and attributes.
- Directory entries can refer to an inode instead of containing attributes.
- Handling long file names in directories can be done in-line or using a heap.
Shared Files
- Shared files can be implemented using a common inode.
- Linking a file creates a new directory entry pointing to the same inode.
- Removing a shared file only removes the directory entry, not the file itself.
Disk Space Management
- Block size affects data rate and disk space efficiency.
- Free space can be managed using a linked list or bit map.
- Quotas can be used to track and limit disk use per user.
File System Reliability
- File systems need to be dumped regularly to ensure reliability.
- Bit maps can be used to keep track of modified files and directories.
- File system states can be consistent, missing a block, or have duplicate blocks.
File System Performance
- The block cache can improve file system performance.
- Log-structured file systems use a log of writes to improve performance.
Example File Systems
CD-ROM File Systems
- CD-ROM file systems use ISO 9660 directory entries.
CP/M File System
- CP/M memory layout includes a directory and file allocation table.
- CP/M directory entries have a specific format.
MS-DOS File System
- MS-DOS directory entries have a specific format.
- Maximum partition sizes depend on block size.
Windows 98 File System
- Windows 98 uses an extended MS-DOS directory entry.
- Long file names are stored in a specific format.
UNIX V7 File System
- UNIX V7 directory entries have a specific format.
- UNIX V7 inodes contain file attributes and disk block pointers.
- Looking up a file involves traversing the directory hierarchy.
An Example Program Using File System Calls
- Example programs can use file system calls to create, read, and write files.
Memory-Mapped Files
- Memory-mapped files can be used to map files into a process's address space.
Directories
Single-Level Directory Systems
- Single-level directory systems have a single directory with all files.
Two-level Directory Systems
- Two-level directory systems have a root directory with subdirectories.
Hierarchical Directory Systems
- Hierarchical directory systems have a tree-like structure.
Path Names
- Path names are used to locate files in a directory hierarchy.
Directory Operations
- Directory operations include create, delete, opendir, closedir, readdir, rename, and link.
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Description
This quiz covers the basics of file systems, including files, directories, and file system implementation. It also touches on long-term information storage and the requirements for it.