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ATA Configurations

Given the timing issues already present in the ATA testing environment, the decision was made to not switch to archive log mode and table and index level logging for the test runs. In addition, the query stream was modified to allow reconnection of the test user between runs to force release of the undo and temporary segments. Why this was required in the ATA testing and not in the SSD testing is unclear but it is probably due to the excessive time required to run most of the ATA queries.

The ATA array was tested for the following configurations:

  • Nologging and noarchive base run

  • Nologging and noarchive

  • Logs and temp files on SSD

  • Data on SSD full buffer memory (1 gigabyte)

  • Data on SSD half buffer memory (500 megabytes)

The results for the queries are shown in Figure 4.2. The percentage difference between SSD and SATA is so large it is not feasible to report them. However, the total elapsed times, adding in a base of 1440 minutes per each non-complete query for the SCSI, show a factor of 179 times difference between the SSD and ATA results in favor of the SSD drives. Remember that the queries for the SSD tests all completed, while several in the ATA tests were halted at the 24 hour point.

Please note that in order to plot the results on a single plot the vertical scale had to be switched to logarithmic. Therefore the changes in query time may only appear to be slight on the graph but may actually be several tens of percentage points. Review the detailed results in Appendix D. The runs not involving the SSD showed consistent results.

When the temp and undo tablespaces were moved to the SSD drives some queries improved while others got worse. When the data tablespace was moved to SSD all query times were improved by an average of 100 percent.

The reduction of db_cache_size by half with the data tablespace on SSD actually shows some improvements in performance on queries 2, 8, 11, 13, 13a while the others performed worse than the full memory levels. However all of the queries performed better with the data on the SSD than the ones on 100% ATA.

Needless to say, concerns about SSD performance were laid firmly and completely to rest when the first query on the SCSI and ATA tests had to be aborted at the 30 hour+ point. While at least a 30% improvement in query speeds was expected based on the previous insert and update based tests, it was a very pleasant surprise when the factor of 176 times improvement for overall query time was revealed.

Next it is time to compare the various SSD and ATA test scenarios.

The above book excerpt is from:

Oracle Solid State Disk Tuning

High Performance Oracle tuning with RAM disk

ISBN 0-9744486-5-6  

Donald K. Burleson & Mike Ault


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