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iostat puzzle



Hi , 

The below is the iostat output redhat linux 3.0 which shows very large 
values for rkB/s field (568785.19 ) 

Reading 568785.19 kB per second! Impossible. 

$uname -a: 
Linux koccrmdev 2.4.21-15.ELsmp #1 SMP Thu Apr 22 00:18:24 EDT 2004 
i686 i686 i386 GNU/Linux 

$ cat /etc/redhat-release 
Red Hat Enterprise Linux ES release 3 (Taroon Update 2) 

I have oracle running on this server. I can basically regenerate this 
pattern easily ,this happens when i disable async. io at oracle part  . 

With aio enabled , oracle does not use pread or readv system calls and 
i see reasonable values at iostat for the system. 

But when i disable it , iostat shows very high values. 

For clarity , when i get these results , the only user on the system is 

me. 

avg-cpu:  %user   %nice    %sys   %idle 
          20.83    0.00   68.98   10.19 

Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s 
avgrq-sz avgqu-sz   await  svctm  %util 
/dev/sda   127851.85 7748.15 14344.44 879.63 1137570.37 69007.41 
568785.19 34503.70    79.25  1966.67   12.91   1.22 1851.85 
/dev/sda1    0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00 
/dev/sda2    0.00   0.00  0.00  0.00    0.00    0.00     0.00     0.00 
   0.00     0.00    0.00   0.00   0.00 
/dev/sda3  127824.07  37.04 14118.52 77.78 1135540.74  918.52 567770.37 

  459.26    80.05  1914.81   13.48   1.30 1851.85 
/dev/sda5   27.78  12.96 18.52  9.26  370.37  177.78   185.19    88.89 
  19.73     2.96   10.67   8.00  22.22 
/dev/sda6    0.00 7698.15 207.41 792.59 1659.26 67911.11   829.63 
33955.56    69.57    48.70    4.89   4.00 400.00 

Can this be a redhat bug? 

Kind Regards, 
tolga 

 



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