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CHAPTER DOWNLOADS Oracle disk I/O tuning: ATA tuning in Windows Mike Ault 08.13.2004 Rating: -2.00- (out of 5) Digg This!     StumbleUpon     Del.icio.us    The following is part of a series on the different aspects of disk I/O performance and optimization for Oracle databases. Each tip is excerpted from the not-yet-released Rampant TechPress book, "Oracle disk I/O tuning," by Mike Ault. Check back to the main series page for upcoming installments. [TABLE]

ATA tuning in Windows

Figure 2-6 shows a screen capture from a seldom used Windows 2000 system drive (all data and file storage is done to a shared file system). Notice even a lightly used drive is showing over 20% fragmentation. On a laptop using NT4.0 SP6a, after two years of work, the drive was 100% fragmented! No wonder performance was terrible.

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Figure 2-6: Disk Fragmentation on Windows

Here is the report that goes along with the display in figure 2-6. In order to fix the above fragmentation, it took multiple passes through the defragmentation routine provided by Windows 2000. The first pass resulted in extreme freespace fragmentation, which would have caused the first file that was written after defragmentation to be fragmented! After 5 passes, the fragmentation was down to 12%, after 9 passes, 10%, which seemed to be the best it could do, leaving 21% of the files fragmented. Figure 2-8 shows the final screen shot after optimization.

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Figure 2-8: Final Defragmentation Screen

The final

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report from the defragmentation utility is shown below. Compare the initial report with the final report and you can see significant reduction in the number of fragments, especially in the directories and system files. To reduce the chance of fragmentation in Windows with Oracle, consider using raw partitions (partitions where Oracle handles the IO to the disk instead of the operating system). Windows uses an optimistic write algorithm that writes blocks back to the first available location, not their original location, causing Windows to fragment from day one of operation.

Some claim that since the file system in Windows (or AIX or VMS) is designed to fragment, it performs better when fragmented. This statement seems odd since every time you defragment in Windows (or AIX or VMS) your performance improves. If this old SA tale where true, wouldn't performance get worse when you defragment?

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About the author

Mike Ault is a SearchOracle.com expert and a senior Oracle consultant with Burleson Consulting, and one of the leading names in Oracle technology. The author of more than 20 Oracle books and hundreds of articles in national publications, Mike Ault has five Oracle Masters Certificates and was the first popular Oracle author with his landmark book "Oracle7 administration and management." Mike also wrote several of the "Exam Cram" books, and enjoys a reputation as a leading author and Oracle consultant. Ask Mike a question today!

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