IV96987: SEVER I/O PERFORMANCE DEGRADATION OF AFDASD AFTER IV51289

APAR status

• Closed as fixed if next.

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

• Corrected problem when reading mode page 20.
  

Problem conclusion

Temporary fix

Comments

• This APAR is being closed FIN. This means that a solution to
  this APAR is expected to be delivered from IBM in a release
  (if any) to be available within the next 24 months.
  

APAR Information

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

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

  IV97010 IV97029 IV97075 IV97111 IV97118 IV97129

Fix information

Applicable component levels