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IV97075: SEVER I/O PERFORMANCE DEGRADATION OF AFDASD AFTER IV51289 APPLIES TO AIX 7200-01

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APAR status

  • Closed as program error.

Error description

  • SAS RAID DISK I/O on AIX V7.1 TL3SP9 is much slower than
on AIX V7.1 TL3SP1, or after installing APAR IV51289.
THe issue is that TCQ depth gets forced to default value
of 1.
The following dd test shows the issue. The data has to be
larger than 1024 MB.

# timex dd if=/dev/zero bs=1M count=1000
 of=/dev/rtestlv
      1000+0 records in
      1000+0 records out

      real 20.16
      user 0.00
      sys  0.23

For reference, the results of AIX V7.1 TL3 SP1 are

      # timex dd if=/dev/zero bs=1M count=1000
of=/dev/rtestlv
      1000+0 records in
      1000+0 records out

      real 7.80
      user 0.00
      sys  0.23

Local fix

  • 



Problem summary


    

  • SISSAS driver/adapter queue depth could get set to 1 instead
of 64, decreasing I/O performance.

    



Problem conclusion


    

  • Correct problem when reading mode page 20.

    



Temporary fix


    

  • 



Comments


    

  • 



APAR Information




    

  • APAR number
    IV97075
    • 

  • Reported component name
    AIX V7.2
    • 

  • Reported component ID
    5765CD200
    • 

  • Reported release
    720
    • 

  • Status
    CLOSED  PER
    • 

  • PE
    NoPE
    • 

  • HIPER
    NoHIPER
    • 

  • Submitted date
    2017-06-08
    • 

  • Closed date
    2017-06-08
    • 

  • Last modified date
    2017-09-25
    • 





    

  • APAR is sysrouted FROM one or more of the following:
    

    
IV96987
    

    • 

  • APAR is sysrouted TO one or more of the following:
    

    • 



Fix information


    

  • Fixed component name
    AIX V7.2
    • 

  • Fixed component ID
    5765CD200
    • 



Applicable component levels


    

  • R720  PSY  U873453
       UP17/09/21  I  1000
    • 



PTF to Fileset Mapping








      
              
                            

              

              [{"Business Unit":{"code":"BU070","label":"IBM Infrastructure"},"Product":{"code":"SSVEF8","label":"AIX 7.2 Enterprise Edition"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"720","Edition":"","Line of Business":{"code":"LOB68","label":"Power HW"}},{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SG11S","label":"AIX 7.2 HIPERS, APARs and Fixes"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"720","Edition":"","Line of Business":{"code":"LOB08","label":"Cognitive Systems"}}]
              

                                                                    

          
 
        

      

    

      

        

          

            
Document Information


            

            


                        

            Modified date:
            

            10 September 2025
            

            
                      

        


        

        


      

    

  



    

  

  
    
            

          
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