High IO Wait - PowerEdge 2650 - Perc 3/Di

Tillotson, Jeff Jeff.Tillotson at KnowledgeStorm.com
Fri Jan 19 11:46:51 CST 2007

>On Fri, Jan 19, 2007 at 09:18:35AM -0500, Tillotson, Jeff wrote:
>> The system is hanging during or after file writes.  If I do something
>> like:
>> dd if=/dev/zero of=/home/jefft/file1 bs=512 count=864000 the system 
>> will eventually hang and come back.  Using sar, iostat, top, I can 
>> watch iowait percentage climb and climb until it hangs.  
>Then, when I 
>> can gain access again, it drops slowly.  The iowait 
>percentage goes up 
>> even after the dd has completed.
>Jeff, another question.  Is this reproduceable every time?  I 
>just tried it on one of our 2650's that had had BIOS updates 
>done, and while I saw some spikes in iowait activity, the 
>system remained useable and the file finished writing without 
>any issue.

Everytime.  The funny thing is the IO Wait continues, and really spikes,
after the copy has completed.  The system never actually crashes it just
"freezes" for a period of time.  

Thanks for everyone's response.  I am trying some of the suggestions
during the day.  Well, except for the don't use PERC controller one :).
My arms aren't that long.  
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