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Re: Vacuum Problem

From: plu tard <plutard12(at)hotmail(dot)com>
To: <pgsql-novice(at)postgresql(dot)org>
Subject: Re: Vacuum Problem
Date: 2007-12-12 09:33:33
Message-ID: BAY108-W81140191E5850D3A4571DA6650@phx.gbl (view raw or flat)
Thread:
Lists: pgsql-novice
I seem to be having a similar problem. I'm trying to run a vacuum full on one
of my development machines and it seems really slow.

Take a look at this 'vmstat 1'  output. It seems to be pegged in iowait:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1 11  34664  55388   6652 1604836    0    0     0     0 1247 3202  1  4  0 95
 0 11  34664  55760   6652 1604836    0    0     0     0 1182 3165  1  4  0 95
 0 11  34664  56256   6652 1604836    0    0     0     0 1227 3296  0  6  0 94
 0 12  34664  56752   6652 1604836    0    0     0     0 1367 3814  1  4  0 95
 0 12  34664  57372   6652 1604836    0    0     0     0 1174 3173  0  3  0 97
 0 12  34664  57868   6652 1604836    0    0     0     0 1229 3169  1  4  0 95
 0 12  34664  58240   6652 1604836    0    0     0     0 1282 3469  0  5  0 95
 0 12  34664  58736   6652 1604836    0    0     0     0 1007 2428  1  4  0 95
 0 12  34664  59232   6652 1604836    0    0     0     0 1246 3205  1  6  0 93
 0 12  34664  59728   6652 1604836    0    0     0     0 1072 2895  1  3  0 96
 0 12  34664  60100   6652 1604836    0    0     0     0 1182 3149  1  4  0 95
 0 12  34664  60720   6652 1604836    0    0     0     0 1232 3352  0  8  0 92
 0 12  34664  61092   6652 1604836    0    0     0     0 1166 2836  1  4  0 95
 0 12  34664  61464   6652 1604836    0    0     0     0 1059 2696  0  3  0 97
 6 12  34664  61960   6652 1604836    0    0     0     0 1066 2471  1  4  0 95
 0 12  34664  62580   6652 1604836    0    0     0     0 1309 3624  1  6  0 93
 0 12  34664  62952   6652 1604836    0    0     0     0 1121 2885  0  4  0 96
 0 12  34664  63324   6652 1604836    0    0     0     0  925 1999  1  5  0 94
 0 12  34664  63944   6652 1604836    0    0     0     0 1102 2938  1  2  0 97
 0 12  34664  64440   6652 1604836    0    0     0    32 1016 2609  1  1  0 98
 0 12  34664  64796   6652 1604836    0    0     0     0 1020 2684  3  6  0 91
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 7 12  34664  65244   6652 1604836    0    0     0     0 1094 3137 10  4  0 86
 0 12  34664  65740   6652 1604836    0    0     0  1144 1135 2932  2  5  0 93
 3 12  34664  64872   6652 1604836    0    0     0  4800 1029 3182 33  9  0 58
 0  9  34664  65740   6652 1604836    0    0     0  6932  814 1931  5  5  0 90
 4  5  34664  65120   6664 1606056    0    0     8  3184  809  813 35 14  0 51
 0  6  34664  45344   6684 1606232    0    0   152 164320 1216  612 19 17  0 64
 1 12  34664  44912   6688 1607888    0    0    44     0  690  899 31 15  0 54
 0 13  34664  44264   6696 1608220    0    0    68     0  983 1508  3  6  0 91
 0 13  34664  43832   6696 1608532    0    0    72     0 1052 1415  6  5  0 89

Is that normal? Does it look like a hardware misconfiguration of some sort?

Running Pg 8.2.5 on Ubuntu 7.04 with 2GB ram.
I have two IDE disks running software RAID 1.

postgresql.conf is hasn't been changed much except I increased
effective_cache_size to 1G. I also tried raising maintenance_work_mem
based on a previous message in this thread, but it didn't seem to make
any improvement.

/sbin/hdparm /dev/hda:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 24792/255/63, sectors = 398297088, start = 0

I have each disk on a separate IDE channel, each configured as master.
One cable has a DVD on it too set as slave.

I have a similar machine, also with two disk RAID 1, and it seems to run
vacuum full much faster. It's on CentOS 4 with Pg 8.2.4. Same config
except it's using effective_cache_size of 2GB with 4GB total ram.

Any ideas for what to investigate?

Thanks.





D

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