Re: PostgreSQL 8.0 occasionally slow down

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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@xxxxxxxxxxxx>:
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


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