Overview
Oracle ASM disk groups are built on a set of Exadata grid disks. Exadata uses ASM disk groups store database files.
ASM Provides 3 Types of Redundancy:
External: ASM doesn’t provide redundancy. External redundancy is not an option on Exadata. You must either use normal or high redundancy.
Normal: It provides two-way data mirroring. It maintains two copies of data blocks in separate failure groups
High: It provides three-way data mirroring. It maintains three copies of data blocks in separate failure groups
Environment
Exadata Database machine X2-2
8 Compute nodes, 14 Storage cells and 2 IB Switch
Steps to create ASM disk Group using ASMCA utility.
Set the environment variable to Grid Home and start asmca
dm01db01-orcldb1 {/home/oracle}:. oraenv
ORACLE_SID = [orcldb1] ? +ASM1
The Oracle base has been changed from /u01/app/oracle to /u01/app/grid
dm01db01-+ASM1 {/home/oracle}:which asmca
/u01/app/12.2.0.1/grid/bin/asmca
dm01db01-+ASM1 {/home/oracle}:asmca
1. Create ASM Disk Group using Normal Redundancy (3 failure groups)
First we will create an ASM disk group using Normal Redundancy using 3 storage cells.
ASMCA starting
Click on ASM Instances on left pane
Here we are running Flex ASM and current ASM instance is running on Nodes 1, 2 and 4
Click on Disk Groups. We can see currently there 2 disk groups one for OCR/Voting disks and another one for MGMT database repository. To create a new disk group click on “Create” button.
Click on “Change Disk Discovery Path”
Enter the following path to discover the grid disks.
Select desired grid disks to create ASM Disk Group.
Here I am creating DATA disk group by selecting DATA grid disks from 3 storage cells
Click on “Show Advanced Options” and select the ASM/Database/ADVM compatibility. Finally click Ok to create DATA disk group
DATA disk group creation in progress
We can now see that the DATA disk group is created
Let’s verify the newly created DATA disk group. Right click on the DATA disk group and select “view status details”
We can see that the DATA disk group is mounted on node 1, 2 and 4
2. Creaet ASM Disk Group Using High Redundancy (5 failure groups)
Now let’s create another ASM disk group using High Redundancy using grid disks from 5 storage cells.
Click Create button to create new ASM disk group
Enter the Disk Group name, select the desired grid disks and ASM/Database/ADVM attributes and click ok
DATA1 disk group creation is in process
We can see that DATA1 disk group created
3. Add disks to ASM Disk Group (add grid disks from one storage cell)
Now let’s Add disks to DATA1 disk group. I am going to add DATA grid disks from a storage to DATA1.
Right click on the DATA1 disk group and select Add Disks
Select the desired grid disks from storage cell and click ok
Disks are being added to DATA1
We can see the size of DATA1 disk group has increased
4. Drop disks from ASM Disk Group (remove grid disks from one storage cell)
This time let’s Drop disks from DATA1 disk group. I am going to remove DATA grid disks from a storage used by DATA1.
Right click on DATA1 disk group and select Drop Disks
Process started
Select the desired Grid disks to be dropped from DATA1 disk group and click ok
Disks are being dropped from DATA1
We can see that the DATA1 disk group size is dropped
Conclusion:
In this article we have learned different ASM disk group redundancy levels and how to create ASM disk group on Exadata using a set of Exadata grid disks. We have created different ASM disk group using different redundancy levels and performed few disk operations like adding and dropping.
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