Re: PostgreSQL 8.0 occasionally slow down

Hi Richard,

Thank for your prompt reply. I have used the command "vmstat 10" to
investigate the I/O issue and listed below :

procs -----------memory---------- ---swap-- -----io---- --system--
----cpu----
r b swpd free buff cache si so bi bo in cs us sy id
wa
0 0 26848 8376 2208 595796 0 0 16 16 14 13 5 2 91
2
1 0 26848 8024 2128 596324 0 0 1595 620 2006 3489 45 7 39
9
2 0 26848 8432 2024 595988 0 0 1399 163 1953 3830 38 8 47
7
2 0 26936 8488 2008 596092 0 0 1696 636 1973 7423 52 8 31
9
1 0 26936 8476 2008 596148 0 0 1237 660 1618 1863 34 6 50
11 <-- The starting time when the pgsql log transaction due to long
execution duration.
0 0 26936 8024 1980 596756 0 0 1983 228 1985 2241 52 8 31
10
0 2 26936 8312 2040 595904 0 0 405 16674 1449 1675 17 6 1
76 <-- The intermediate time reaching I/O peak.
0 0 26936 8544 2088 594964 0 0 1191 8295 680 1038 30 4 13
53
2 0 26936 8368 2124 595032 0 0 517 935 866 985 14 3 79
4
0 0 26936 8368 2064 595228 0 0 1706 190 1979 2356 45 7 38
9
0 0 26936 8196 2132 595452 0 0 1713 642 1913 2238 44 8 37
11
1 1 26936 8164 2168 595512 0 0 1652 666 2011 2542 45 7 38
10
0 1 26936 8840 2160 594592 0 0 1524 228 1846 2116 42 8 43
7
0 0 26936 7384 2200 596304 0 0 1584 604 1972 2137 41 7 40
11

As you said, it seems for each 3~4 minutes, there is a I/O peak. But what is
the problem indicating by it ?

Thanks for help.
Twinsen

2007/6/28, Richard Huxton <dev(at)archonet(dot)com>:
>
> Ho Fat Tsang wrote:
> > Hi Richard,
> >
> > I have tuned the checkpoint_timeout to 30 second which is ten times
> less
> > than default and the issue is still reproduced. Do you have any
> recommended
> > configuration for WAL ?
>
> If you look at the output of "vmstat 10" and "iostat -m 10" (I'm
> assuming you're on Linux) does it show your I/O peaking every three
> minutes? I might have been wrong about the cause.
>
> --
> Richard Huxton
> Archonet Ltd
>