SUMMARY: wait io and SAN

From: <Samier.Kesou_at_bfa.de>
Date: Thu Feb 13 2003 - 04:36:09 EST
hi,

thanks all who replied.

Darren Dunham pointed out,  that wait io on a system with

fast disks doesnt mean that the amount of requested io is very high

so the disks are not slow.



joe fletcher reported about a similar experience but they found out

that the reporting tool did wrong reporting instead of the disks being slow
.

I read a similar thing on the internet pointing to mpstat not reporting
correct.



Some pointed to the hba and and said to get a new driver update.



Others reminded that parallel to tuning the san side you can tune

the oracle side. On www.orafaq.org is a good paper on the aspects of

tuning oracle in a san enviroment.



the tool to use is iostat to see the amount of wait queue and the

percentage of disk usages. on the san side this would be

symstat.



thanks

samier.




                                                                                                        
                                                                                                        
                      Samier.Kesou@bfa.de      An:       sunmanagers@sunmanagers.org                    
                      Gesendet von:            Kopie:                                                   
                      sunmanagers-admin@sunm   Thema:    wait io and SAN                                
                      anagers.org                                                                       
                                                                                                        
                                                                                                        
                      12.02.2003 13:38                                                                  
                                                                                                        
                                                                                                        




Hello,

we have a 12 CPU Server with a oracle database running on it
OS: 5.8
oracle:8.1.7
SAN: EMC Symmetrix
HBA: Emulex
when running batch jobs we experience high values of wait io
on all CPU's (20 - 60 % using mpstat). The amount for every single CPU is
about the same.
Performance checks on the SAN side didn't show any performance
problems.

I would have thought that SAN disks would have a better performance than
that.
Has anyone a similar experience or information about finding the cause
of the wait io?

thanks in advance,
Samier.
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Received on Thu Feb 13 04:41:39 2003

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