Oracle RAC ASM Disk Space Test
ASM is a volume manager and a file system for Oracle database files that supports single-instance Oracle Database and Oracle Real Application Cluster (Oracle RAC) configuration. ASM is Oracle’s recommended storage management solution that provides an alternative to conventional volume managers, file systems, and raw devices.
ASM uses disk groups to store datafiles; an ASM disk group is a collection of disks that ASM manages as a unit. Within a disk group, ASM exposes a file system interface for Oracle database files. The content of files that are stored in a disk group are evenly distributed, or striped, to eliminate hot spots and to provide uniform performance across the disks.
To ensure that a disk group always has sufficient space to store the critical organizational data, you will have to continuously track the space usage of the disk group. This will provide you with early pointers to potential space contentions and help you swiftly provide more space to the group by adding more disks. The ASM Disk Space test enables you to achieve this end. This test closely monitors how each disk in a disk group uses the space available to it, points you to the disks that are running out of space, and thus holds a mirror to space contentions on a disk group.
This test is disabled by default. To enable the test, go to the enable / disable tests page. To access this page, follow the Tests -> Enable/Disable menu sequence in the Agents tile of the Admin tile menu. In the enable/disable tests page, pick Oracle Cluster as the Component type, Performance as the Test type, choose this test from the disabled tests list, and click on the < button to move the test to the ENABLED TESTS list. Finally, click the Update button.
Target of the test : Oracle RAC
Agent deploying the test : An internal agent
Outputs of the test : One set of results for each DiskGroup:Disk pair on the Oracle server being monitored
|
Measurement | Description | Measurement Unit | Interpretation |
---|---|---|---|
Used space: |
Indicates the amount of space currently used in this disk. |
MB |
Ideally, the value of this measure should be low. A consistent increase in this value is a cause for concern. |
Free space: |
Indicates the amount of space in this disk that is currently free - i.e., available for use. |
MB |
Ideally, the value of this measure should be high. A consistent decrease in this value is a cause for concern. |
Space availability: |
Indicates the percentage of space in this disk that is currently unused.
|
Percent |
A high value is typically desired for this measure. By comparing the value of this measure across disks and across disk groups, you can quickly isolate the disks/groups that are running short of space. If the free space is alarmingly low for all disks in a group, it indicates that the group requires more space. You can then consider making space by adding more disks to the group. |
Space usage: |
Indicates the percentage of space in this disk that is currently used.
|
Percent |
A low value is typically desired for this measure. By comparing the value of this measure across disks and across disk groups, you can quickly isolate the disks/groups that are utilizing space excessively. If the used space is alarmingly high for all disks in a group, it indicates that the group is rapidly running out of space. You can then consider making space by adding more disks to the group. |
Used space growth: |
Indicates the growth in space usage of this disk since the last measurement period. |
MB/Sec |
If you observe the variations to this measure over time, you will be able to detect early whether the space in the disk is being steadily eroded or not. This way, you can initiate measures to conserve space much before the disk exhausts all the space available to it. |
If you observe the variations to this measure over time, you will be able to detect early whether the space in the disk is being steadily eroded or not. This way, you can initiate measures to conserve space much before the disk exhausts all the space available to it.