Well, it took a while but I finally have the results of Satoshi's PCTFree patch back from the STP. Bad news about the STP, see below ...
Anyway, a series of DBT2 runs doesn't seem to show any advantage to PCTFree over a 3-hour run with no vacuums:
test# pctfree full_page_writes notpm 303164 off off 1803 303165 on on 1847 303166 on off 1860 303167 off on 1801 303168 off off 1838 303169 on on 1821 303170 on off 1846
The differences above are small enough to be in the "noise" factor of DBT2 execution. The good news is that it appears that stuff which has been done since July has lessened the penalty for checkpoints somewhat; while the maximum response time is still better on the full_page_writes=off systems, the average throughput is no longer substantially different. Either that, or full_page_writes=off isn't working properly anymore.
If anyone has suggestions on different tests to run, or better stats to compile, please speak up.
Now, the bad news: the STP has had some failures and is down to *one* usable machine for testing. I have, like, 160 performance tests backed up which are never going to get run before we release 8.1. I'm going to be hitting up some major PostgreSQL sponsors for hardware donations, any help is welcome.
-- --Josh
Josh Berkus Aglio Database Solutions San Francisco
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