Tom, > This will remove just the CRC calculation work associated with backed-up > pages. Note that any attempt to recover from the WAL will fail, but I > assume you don't need that for the purposes of the test run.
Looks like the CRC calculation work isn't the issue. I did test runs of no-CRC vs. regular DBT2 with different checkpoint timeouts, and didn't discern any statistical difference. See attached spreadsheet chart (the two different runs are on two different machines). I think this test run http://khack.osdl.org/stp/302903/results/0/, with a 30-min checkpoint shows pretty clearly that the behavior of the performance drop is consistent with needing to "re-prime" the WAL will full page images. Each checkpoint drops performance abruptly, and then slowly recovers until the next checkpoint. Do note that there is a significant statistical variation in individual runs. It's only the overall trend which is significant. -- --Josh Josh Berkus Aglio Database Solutions San Francisco
crc_patch_test.pdf
Description: Adobe PDF document
---------------------------(end of broadcast)---------------------------
TIP 4: Have you searched our list archives?
http://archives.postgresql.org
