IJ51830: UNMIRRORING PASSIVE MWC LV CAN LEAVE DIRTY BIT SET ON DISK APPLIES TO AIX 7200-05

APAR status

• Closed as program error.

Error description

• Unmirroring an LV with Passive MWC while the LV is open
  can leave the dirty bit set on disk, even after the LV
  is closed.
  If the LV is in a VG managed by PowerHA, then during a
  subsequent failover, LVM may interpret that bit to mean
  that the system crashed with the LV open, and it needs
  to be put into passive recovery mode.
  However the LV can never be resyncd (because it is no
  longer
  mirrored), so it remains in passive recovery mode.
  This can have an unexpected impact on I/O performance.
  

Local fix

Problem summary

• rmlvcopy does not clear the lv passive mwc 'dirty bit' when
  unmirroring the LV.
  mklvcopy does not set the lv passive mwc 'dirty bit' for LVs
  that are already open when they're mirrored.
  PowerHA bringing VG online can set the LV into passive
  recovery mode unnecessarily for unmirrored LVs
  The combination of these above issues can result in LV
  being set in passive recovery mode even if it is unmirrored,
  incurring unnecessary overhead to I/O.
  

Problem conclusion

• Fix the above issues.
  

Temporary fix

Comments

• 7200-05 - use AIX APAR IJ51830
  7300-03 - use AIX APAR IJ51812
  

APAR Information

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

  IJ51654

• 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