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Re: Bad iostat numbers

From: David Boreham <david_list(at)boreham(dot)org>
To: carlos(dot)reimer(at)opendb(dot)com(dot)br
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Bad iostat numbers
Date: 2006-12-01 02:24:34
Message-ID: 456F9262.4080207@boreham.org (view raw or flat)
Thread:
Lists: pgsql-performance
Carlos H. Reimer wrote:

>  
>
> avg-cpu:  %user   %nice %system %iowait   %idle
>
>           50.40    0.00    0.50    1.10   48.00
>
>  
>
> Device:    rrqm/s wrqm/s   r/s   w/s  rsec/s  wsec/s    rkB/s    wkB/s 
> avgrq-sz avgqu-sz   await  svctm  %util
>
> sda          0.00   7.80  0.40  6.40   41.60  113.60    20.80    
> 56.80    22.82 570697.50   10.59 147.06 100.00
>
> sdb          0.20   7.80  0.60  6.40   40.00  113.60    20.00    
> 56.80    21.94 570697.50    9.83 142.86 100.00
>
> md1          0.00   0.00  1.20 13.40   81.60  107.20    40.80    
> 53.60    12.93     0.00    0.00   0.00   0.00
>
> md0          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
>
>  
>
> Are they not saturated?
>
>  
>
> What kind of parameters should I pay attention when comparing SCSI 
> controllers and disks? I would like to discover how much cache is 
> present in the controller, how can I find this value from Linux?
>
>
These number look a bit strange. I am wondering if there is a hardware 
problem on one of the drives
or on the controller. Check in syslog for messages about disk timeouts 
etc. 100% util but 6 writes/s
is just wrong (unless the drive is a 1980's vintage floppy).



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