AIX: ASM Metadata & DISKS

lspv: command used to get disk list (disk, assigned PVID, vg, status)


$lspv
hdisk0          00c2e2503cddd971                    rootvg          active
hdisk9          00c2e2508b71c3a9                    sw_vg           active
hdisk1          none                                None          
hdisk2          none                                None          
hdisk3          none                                None          
...

ASM disks should not have PVID assigned to them (Configuring Storage for Grid Infrastructure, 3.3.3 Configuring Disk Devices for Oracle ASM, step 7). They should be removed with fallowing command before assigned to ASM:

$/usr/sbin/chdev -l hdiskn -a pv=clear

Note: If you already assigned disks without clearing PVID, don't clear it using above command. It corrupts asm disks while clearing header. Because it is the same header where asm keeps its internal info. Actually ASM clears header and PVID and writes its own header when a disk assigned to a datagroup. However because OS odm (aix's internal database) is not updated, you can see PVIDs using lspv although it is not there.

By using following command you can query disk header in order to see ASM internal information written on disk (requires root permission)


$lquerypv -h /dev/rhdisk5
00000000 00820101 00000000 80000000 81AA935B |...............[|
00000010 00000000 00000000 00000000 00000000 |................|
00000020 4F52434C 4449534B 00000000 00000000 |ORCLDISK........|
00000030 00000000 00000000 00000000 00000000 |................|
00000040 0A100000 00000103 54455354 5F303030 |........TEST_000|
00000050 30000000 00000000 00000000 00000000 |0...............|
00000060 00000000 00000000 54455354 00000000 |........TEST....|
00000070 00000000 00000000 00000000 00000000 |................|
00000080 00000000 00000000 54455354 5F303030 |........TEST_000|


In 11g you can backup and recover corrupted disk headers using md_backup and md_restore. The corrupted diskgroup must be specified with the ‘-g’ flag for the restore to complete
successfully:

ASMCMD> md_restore -b /oracle/backup/asm_metadata020409.bkp -g 'TEST'

Ref:
11gRAC_ASM_1.pdf (doc link)