On 6/16/10 12:00 PM, Josh Berkus wrote:
* fsync=off => 5,100
* fsync=off and synchronous_commit=off => 5,500
Now, this *is* interesting ... why should synch_commit make a difference
if fsync is off?
Anyone have any ideas?
I found that pgbench has "noise" of about 20% (I posted about this a couple days ago using data from 1000 identical pgbench runs). Unless you make a bunch of runs and average them, a difference of 5,100 to 5,500 appears to be meaningless.
Craig
tmpfs, WAL on same tmpfs:
* Default config: 5,200
* full_page_writes=off => 5,200
* fsync=off => 5,250
* synchronous_commit=off => 5,200
* fsync=off and synchronous_commit=off => 5,450
* fsync=off and full_page_writes=off => 5,250
* fsync=off, synchronous_commit=off and full_page_writes=off => 5,500
So, in this test, it seems like having WAL on tmpfs doesn't make a
significant difference for everything == off.
I'll try running some tests on Amazon when I have a chance. It would be
worthwhile to get figures without Python's "ceiling".
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