QCR, Voting Disk & Quorum failure group in ASM
Voting Disk and Oracle Cluster Registry (OCR) can store inside of an Automatic Storage Management(ASM) Disk Group in Oracle 11gR2.
Oracle Cluster Registry (OCR)
OCR is striped and mirrored similar as ordinary Database Files.
So we can now have option the mirroring capabilities of ASM to mirror the OCR also, without having to use multiple RAW devices for that purpose only.
The Oracle RAC configuration information repository that manages information about the cluster node list and instance-to-node mapping information.
Oracle Clusterware rely on ASM to access the OCR and SPFILE. The OCR and SPFILE are stored similar to how Oracle Database files are stored.
Voting disk is not striped but put as a whole on ASM Disks
if we use a redundancy of normal on the Diskgroup, 3 Voting Files are placed, each on one ASM Disk into a different failgroup.
Therefore, you need to have at least 3 failgroups for that diskgroup, like on this picture:
Quorum failure group
A quorum failure group is a special type of failure group that does not contain user data. Quorum failure groups are used for storing Oracle ASM metadata.
A quorum failure group may also contain voting files if those files are stored in a disk group that contains a quorum failure group.
Note: COMPATIBLE.ASM disk group compatibility attribute must be set to 11.2 or greater to store OCR or voting disk data in a disk group.
Check the disk having voting disk
Select name,voting_file from $asm_disk where VOTING_FILE = 'Y';
Check fail-group type
Select FAILGROUP_TYPE from V$ASM_DISK ;
select FAILGROUP_TYPE from V$ASM_DISK_STAT;
if our ASM Diskgroups consist of only 2 ASM Disks respectively only 2 failgroups like with Extended RAC! Therefore, the new quorum failgroup clause was introduced:
Create Quoram failgroup in diskgroup
create diskgroup data normal redundancy
failgroup fg1 disk 'ORCL:ASMDISK1'
failgroup fg2 disk 'ORCL:ASMDISK2'
quorum failgroup fg3 disk 'ORCL:ASMDISK3'
attribute 'compatible.asm' = '184.108.40.206.0';
FAILGROUP fg3 above needs only one small Disk (300 MB should be on the safe side here, since the Voting File is only about 280 MB in size) to keep one Mirror of the Voting File.
fg1 and fg2 will contain each one Voting File and all the other stripes of the Database Area as well, but fg3 will only get that one Voting File.
Check the quorum disk
select b.name group_name, a.PATH, a.TOTAL_MB, a.failgroup_type
from v$asm_disk a, v$asm_diskgroup b where a.group_number = b.group_number and a.group_number = 1;
GROUP_NAME PATH TOTAL_MB FAILGROUP_TYPE ---------- ------------- -------- -------------- DATA1 ORCL:ASMDISK3 2047 REGULAR DATA1 ORCL:ASMDISK4 2047 REGULAR DATA1 ORCL:ASMDISK5 2047 QUORUM
Note: In 11gR2 Voting file backup is done with QCR backup. It’s not supported manually dd backup.