Database Reference
In-Depth Information
Choose ASM for OCR and Voting Disk at GI Installation
On different Oracle Clusterware releases, storage for OCR and voting disk varies: raw devices on 10gR2, block devices
on 11gR1. Starting with 11g R2, OCR file and voting disk files can be stored in ASM. Unless you are upgrading your
Clusterware from 11gR1 to 11gR2 where you can keep the voting disk in the block device, you should put the voting
disk file in ASM. OCR and voting disk files can be stored in the same ASM diskgroup as Oracle Database files or in a
separate ASM diskgroup. The ASM diskgroup that stores voting disk files can be configured with one of the following
three redundancy level settings. These are similar to a regular diskgroup for database files, but their requirement for
the minimum numbers of failure groups is higher than those diskgroups that only store database files. The number of
the voting disk files is determined by the number of the failure groups of the ASM diskgroup that stores the voting disk
files:
1.
External Redundancy
: no mirroring; only one failure group is needed. This provides only
one copy of the voting disk file. It is strongly recommended to have an external RAID
configuration for this setting.
2.
Normal Redundancy
: at least three failure groups are needed. This provides three copies of
the voting disk files.
3.
High Redundancy
: at least five failure groups needed. This provides five copies of the
voting disk files.
If you decide to store the voting disk file in the same ASM diskgroup as the data files, adding an additional
failure group could mean adding a huge disk space, which you may not have. To solve this problem, a new
quorum failure group is introduced. When this new failure group is added to a diskgroup, it is only used to store
an extra copy of voting disk file, and non-database files will be stored in this failure group. As a result, the size
of the disk for this failure group can be much smaller than other disks in the ASM diskgroup. For example, the
ASM disk for a quorum failure group can be as small as 300MB to cover the 200MB voting disk file. The following
example shows how to use the quorum failgroup clause to include a quorum failure group in a diskgroup:
CREATE DISKGROUP data NORMAL REDUDANCY
FAILGROUP fg1 DISK 'ORCL:DATA1'
FAILGROUP fg1 DISK 'ORCL:DATA2'
QUORUM FAILGROIUP fg3 DISK 'ORCL:OCR1'
ATTRIBUTE 'compatible.asm' = 12.1.0.0.0;
In this case DISK ORCL:DATA1 and ORCL:DATA2 can be 200GB each, DISK ORCL:OCR1 can be small as 300MB.
During the Grid Infrastructure installation you will be asked to provide the disks to create the ASM diskgroup
for OCR and voting disk files (Figure
5-10
). You have an option to select the redundancy level setting of the ASM
diskgroup for OCR and voting disks.
