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From:Phil Date:July 21 2008 10:57am
Subject:Major Performance Degradation after replacing Hard Drive
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Hi All,


Given a fairly simple table as follows

CREATE TABLE `common_userx2` (
  `t_proj` char(6) default NULL,
  `t_id` int(11) NOT NULL default '0',
  `t_nick` varchar(50) character set latin1 collate latin1_bin NOT NULL
default '',
  `t_country` varchar(50) NOT NULL default '',
  `t_cpid` varchar(50) NOT NULL default '',
  `t_url` varchar(50) default NULL,
  `t_create_date` int(11) default NULL,
  `t_create_time` bigint(20) NOT NULL,
  `t_has_profile` char(1) NOT NULL,
  `t_team0` int(11) default NULL,
  `t_metric1` double(20,6) NOT NULL default '0.000000',
  `t_metric2` double NOT NULL default '0',
  `t_metric3` double NOT NULL default '0',
  `t_metric4` double default NULL,
  `t_active` char(1) NOT NULL default '',
  `t_rev_metric1` double(20,6) NOT NULL default '10000000000.000000',
  `t_projrank0` int(11) default NULL,
  `t_rev_metric2` double(20,6) NOT NULL default '10000000000.000000',
  `t_racrank0` int(11) default NULL,
  `t_teamrank0` int(11) default NULL,
  `t_countryrank0` int(11) default NULL,
  `t_createdaterank0` int(11) default NULL,
  PRIMARY KEY  (`t_id`),
  KEY `prank` (`t_rev_metric1`,`t_id`),
  KEY `trank` (`t_team0`,`t_rev_metric1`,`t_id`),
  KEY `countryrank` (`t_country`,`t_rev_metric1`,`t_id`),
  KEY `createdaterank` (`t_create_date`,`t_rev_metric1`,`t_id`),
  KEY `racrank` (`t_rev_metric2`,`t_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1

I have a ranking update statement as follows

set @rank = 0;
update common_userx2 set projrank0 = @rank:=@rank+1 order by
t_rev_metric1,t_id;

For the largest case this has close to 1M rows.

For weeks it was taking around 10seconds to do this. Yesterday I replaced
the main data drive in the machine with a faster SATA Raptor drive. No
problems occurred, but since then (and the subsequent reboot of the machine)
this particular query is taking 45 minutes!

I can't, for the life of me figure out why performance would be degraded so
much. At first I thought perhaps it might be just disk/mysql caching but the
performance has not increased any in subsequent runs.

Any advice on where to look ?

Phil

-- 
Help build our city at http://free-dc.myminicity.com !

Thread
Major Performance Degradation after replacing Hard DrivePhil21 Jul
  • Re: Major Performance Degradation after replacing Hard DriveAnanda Kumar21 Jul
    • Re: Major Performance Degradation after replacing Hard DrivePhil21 Jul
      • Re: Major Performance Degradation after replacing Hard DriveAnanda Kumar21 Jul
        • Re: Major Performance Degradation after replacing Hard DrivePhil21 Jul
      • Re: Major Performance Degradation after replacing Hard DriveBrent Baisley21 Jul
        • Re: Major Performance Degradation after replacing Hard Drivemos21 Jul
        • Re: Major Performance Degradation after replacing Hard DriveWm Mussatto21 Jul
          • Re: Major Performance Degradation after replacing Hard DrivePhil22 Jul