Did you test with full_page_writes on and off? ---------------------------------------------------------------------------
Josh Berkus wrote: > 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 [ Attachment, skipping... ] > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
