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Suppose that you have a UNIX file system where the disk block size is 4096 bytes. Disk addresses and file block pointers take 32 bits (4

Suppose that you have a UNIX file system where the disk block size is 4096 bytes. Disk addresses and file block pointers take 32 bits (4

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
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**Understanding UNIX File System I/O Operations** In a UNIX file system, the disk block size is typically 4096 bytes. Disk addresses and file block pointers are 32 bits (or 4 bytes). An i-node, which stores file attributes and disk block addresses, contains 12 direct pointers, one single-indirect pointer, and one double-indirect pointer. For simplicity, let's assume the index block size is the same as a data block (both are 4096 bytes). Now, let's consider a file that has 50,000 bytes of data and has never been accessed before. We assume only the file's i-node is in memory, and none of the file data blocks are. Thus, to read the entire file into memory, we must determine the number of I/O operations needed. ### Breakdown: 1. **Direct Pointers:** - Each direct pointer can address one block of 4096 bytes. - With 12 direct pointers: \[ 12 \times 4096 \text{ bytes} = 49,152 \text{ bytes} \] - The direct pointers can address up to 49,152 bytes of the file, which is sufficient since the file size is 50,000 bytes. ### Calculation of I/O operations: - Loading the initial 12 blocks through direct pointers requires 12 I/O operations. - Any extra bytes beyond 49,152 bytes (i.e., \(50,000 - 49,152 = 848\) bytes) would need another block. As the file size does not exceed the capability of direct pointers, we do not need to consider the single or double-indirect blocks. Hence the total I/O operations to read the entire file of 50,000 bytes using the 12 direct pointers is: **Answer:** \[ \boxed{12} \] ### Question and Answer: Suppose that you have a UNIX file system where the disk block size is 4096 bytes. Disk addresses and file block pointers take 32 bits (4 bytes), and the i-node contains 12 direct pointers, one single-indirect pointer, and one double-indirect pointer. Assume an index block is the same size as a data block (both 4096 Bytes). If there is a file having 50,000 bytes of data and it is never been accessed, we only assume the file's i-node is in memory, but none of the
Transcribed Image Text:**Understanding UNIX File System I/O Operations** In a UNIX file system, the disk block size is typically 4096 bytes. Disk addresses and file block pointers are 32 bits (or 4 bytes). An i-node, which stores file attributes and disk block addresses, contains 12 direct pointers, one single-indirect pointer, and one double-indirect pointer. For simplicity, let's assume the index block size is the same as a data block (both are 4096 bytes). Now, let's consider a file that has 50,000 bytes of data and has never been accessed before. We assume only the file's i-node is in memory, and none of the file data blocks are. Thus, to read the entire file into memory, we must determine the number of I/O operations needed. ### Breakdown: 1. **Direct Pointers:** - Each direct pointer can address one block of 4096 bytes. - With 12 direct pointers: \[ 12 \times 4096 \text{ bytes} = 49,152 \text{ bytes} \] - The direct pointers can address up to 49,152 bytes of the file, which is sufficient since the file size is 50,000 bytes. ### Calculation of I/O operations: - Loading the initial 12 blocks through direct pointers requires 12 I/O operations. - Any extra bytes beyond 49,152 bytes (i.e., \(50,000 - 49,152 = 848\) bytes) would need another block. As the file size does not exceed the capability of direct pointers, we do not need to consider the single or double-indirect blocks. Hence the total I/O operations to read the entire file of 50,000 bytes using the 12 direct pointers is: **Answer:** \[ \boxed{12} \] ### Question and Answer: Suppose that you have a UNIX file system where the disk block size is 4096 bytes. Disk addresses and file block pointers take 32 bits (4 bytes), and the i-node contains 12 direct pointers, one single-indirect pointer, and one double-indirect pointer. Assume an index block is the same size as a data block (both 4096 Bytes). If there is a file having 50,000 bytes of data and it is never been accessed, we only assume the file's i-node is in memory, but none of the
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