Consider a RAID-4 disk configuration involving five disks A, B, C, D and E where disk E stores the parity. Examine the folowing six scenarios involving read and write operations in the presence of disk failures in this configuration: 1. All disks are up. There is a write operation on block 10 of disk C. 2. Disk B is down and all other disks are up. There is a read operation on block 20 of disk C. 3. Disk C is down and all other disks are up. There is a read operation on block 30 of disk C. 4. Disk D is down and all other disks are up. There is a write operation on block 40 of disk C. 5. Disk E is down and all other disks are up. There is a read operation on block 50 of disk C. 6. Disk E is down and all other disks are up. There is a write operation on block 60 of disk C. In each of the above scenarios determine how many disk accesses happen in order to process the /O operation. Assume that the goal is to allow as many of the l/O operations as possible, in the presence of disk failures. When counting disk accesses do not count accesses to disks that are down. A. The number of disk accesses for the first scenario is 2. B. The number of disk accesses for the second scenario is 2. C. The number of disk accesses for the first scenario is 1. D. The number of disk accesses for the third scenario is 4.
Consider a RAID-4 disk configuration involving five disks A, B, C, D and E where disk E stores the parity. Examine the folowing six scenarios involving read and write operations in the presence of disk failures in this configuration: 1. All disks are up. There is a write operation on block 10 of disk C. 2. Disk B is down and all other disks are up. There is a read operation on block 20 of disk C. 3. Disk C is down and all other disks are up. There is a read operation on block 30 of disk C. 4. Disk D is down and all other disks are up. There is a write operation on block 40 of disk C. 5. Disk E is down and all other disks are up. There is a read operation on block 50 of disk C. 6. Disk E is down and all other disks are up. There is a write operation on block 60 of disk C. In each of the above scenarios determine how many disk accesses happen in order to process the /O operation. Assume that the goal is to allow as many of the l/O operations as possible, in the presence of disk failures. When counting disk accesses do not count accesses to disks that are down. A. The number of disk accesses for the first scenario is 2. B. The number of disk accesses for the second scenario is 2. C. The number of disk accesses for the first scenario is 1. D. The number of disk accesses for the third scenario is 4.
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
Problem 1PE
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Transcribed Image Text:Consider a RAID-4 disk configuration involving five disks A, B, C, D and E where disk E stores the parity. Examine the following six scenarios involving read and write operations in the presence of disk failures in this
configuration:
1. All disks are up. There is a write operation on block 10 of disk C.
2. Disk B is down and all other disks are up. There is a read operation on block 20 of disk C.
3. Disk C is down and all other disks are up. There is a read operation on block 30 of disk C.
4. Disk D is down and all other disks are up. There is a write operation on block 40 of disk C.
5. Disk E is down and all other disks are up. There is a read operation on block 50 of disk C.
6. Disk E is down and all other disks are up. There is a write operation on block 60 of disk C.
In each of the above scenarios determine how many disk accesses happen in order to process the I/O operation. Assume that the goal is to allow as many of the I/O operations as possible, in the presence of disk
failures. When counting disk accesses do not count accesses to disks that are down.
OA. The number of disk accesses for the first scenario is 2.
OB. The number of disk accesses for the second scenario is 2.
OC. The number of disk accesses for the first scenario is 1.
OD. The number of disk accesses for the third scenario is 4.
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