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  3. You are the administrator of a SQL Server 2000 computer. You are configuring a database for an inventory application. The hard d

You are the administrator of a SQL Server 2000 computer. You are configuring a database for an inventory application. The hard d

admin2009-05-19  58
问题 You are the administrator of a SQL Server 2000 computer. You are configuring a database for an inventory application. The hard disks on your server are configured as shown in the exhibit.


The operating system files are located on drive C. Your database will store a maximum of 6 GB of data and requires a maximum of 2 GB of disk space for the transaction log.
You want to optimize database performance. What should you do?
选项 A、Add a 2-GB transaction log to drive D, a 3-GB data file to drive E, and a 3-GB data file to drive F
B、Add a 1-GB transaction log to drive C, a 1-GB transaction log to drive D, a 3-GB data file to drive E, and a 3-GB data file to drive F
C、Add a 1-GB transaction log to drive E, a 1-GB transaction log to drive F, a 3-GB data file to drive E, and a 3-GB data file to drive F
D、Add a 2-GB transaction log to drive F, a 3-GB data file to drive D, and a 3-GB data file to drive E
答案D
解析 Explanation: Basically there are two methods to improve performance in this scenario:

Method 1: put the transaction log file on a separate physical disk.
One way to improve performance and recoverability of your database is to place the data files and the transaction log files on separate disk subsystems, and to use dedicated disks for your data files so that data read and write (I/O) requests are not competing with other I/O requests on those disks. This is (A).

Method 2: data files split across two physical disks
Splitting your data files among a number of disks results in increased I/O performance in particular when multiple controllers are used like in this scenario. This is (D).

To decide which is better we must think about the application. This is an inventory system and we can assume that the queries would be more frequent than additions and update of rows. So we should choose method 2 since it gives the best performance for reading data.

Note: Physical database design involves mapping the logical design onto physical media to allow for the data to be physically accessed and maintained as quickly as possible by taking advantage of the available hardware and software features.

It is important to correctly design the database and to take advantage of hardware and software features early in the development cycle of a database application, because making changes to these components at a later stage it is difficult. Placing log files and the data files on different physical disks, and placing the log file of a drive that does not hold the operating system can improve database performance as it allows the frequently written to log file to exist a disk with its own read/write heads.

Incorrect Answers:
A: In an inventory system data is read more frequently and not so many changes are made to the database. We should optimize the data files not the log file.

B: Placing log files and the data files on different physical disks and placing the log file of a drive that does not hold the operating system can improve database performance as it allows the frequently written to log file to exist a disk with its own read/write heads. In this part of the log file is placed on drive C, which would also hold the operating system.

C: Placing log files and the data files on different physical disks can improve database performance as it allows the frequently written to log file to exist a disk with its own read/write heads. In this solution the log file and the data file are placed on the same physical drive.
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