High IO Wait - PowerEdge 2650 - Perc 3/Di

Tillotson, Jeff Jeff.Tillotson at KnowledgeStorm.com
Wed Jan 24 13:00:17 CST 2007

>Tillotson, Jeff wrote:
>> Hello all,
>> I have a Dell 2650 with a RAID1 drive connected to a Dell PowerEdge 
>> Expandable RAID controller 3/Di on a SuSE Enterprise Linux 
>9.3 server 
>> running 2.6.5-7.283-bigsmp #1 SMP Wed Nov 29 16:55:53 UTC 2006 i686 
>> i686
>> i386 GNU/Linux.
>> 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.
>> I have updated the PERC's firmware to
>> There is no error messages in dmesg, log messages or anyplace else.  
>> Is there some mechanism for tuning this?  Any help would be greatly 
>> appreciated.
>Is swap usage low?  Do kscand and kswapd consistently show 
>high in the list on top when sorted by CPU usage?
>Try re-nicing kscand to 19 and observe the effect.  If that 
>doesn't cause any problems, then re-nice kswapd to 19.
>The above can be dangerous to do if swap usage is high so be careful!

Swap usage is low.  In fact, certain instances of this test have no swap
being used.  I have also tried the test with all swap disabled.  Results
are always the same.  

I have also tried re-nicing several process but the results are always
the same.  

Thanks for you response,
The information contained in this e-mail and attachments, if any, is confidential and may be subject to legal privilege. If you are not the intended recipient, you must not use, copy, distribute or disclose the e-mail and its attachment, or any part of its content or take any action in reliance of it. If you have received this e-mail in error, please e-mail the message back to the sender by replying and then deleting it. We cannot accept responsibility for loss or damage arising from the use of this e-mail or attachments, and recommend that you subject these to your virus checking procedures prior to use.

More information about the Linux-PowerEdge mailing list