Thursday, October 25, 2012

AIX ASM Diskgroup reporting wrong Lun size

  We discovered this strange problem while trying to convert one of our big databases from file system to ASM. After we assigned a 1TB lun to AIX and created a diskgroup on top of it. ASM reporting wrong disk size on it. ASM only be able to detect around 100G out of 1TB.
  After a few poke around to make sure we didn't make any mistake provision the storage to the OS. I did some research on Metalink. And fair enough, I found this is a known bug on AIX ASM

Bug 9495887 AIX: ASM does not recognize correct diskgroup size for large disks

Device         Size (GB)  Paths  Vol Name       Vol Id   XIV Id   XIV Host     
/dev/hdisk4    1135.7     5/5    hedata16     113      7825812  heproddb102

--------------- ----------------- ------------ ---------- ---------- ----- ------ 
TEST_0000       /dev/rhdisk4                 5     101920     101800    60     10 

The workaround suggested was to create the disk group with specific size like following

SQL> create diskgroup DATA external redundancy disk '/dev/rhdisk4' size 1135G;

Frankly it's quite surprising we still hit such basis bugs on AIX ASM even after it was released 3 years. 1TB disk is hardly a large disk nowadays, I guess AIX is just such an unpopular OS for Oracle installation and have very little customer base. And I can totally understand why.