In environments where Oracle Automatic Storage Management (ASM) is used alongside multipath configurations, it's essential to ensure proper integration between ASM and multipath. Incorrect configuration may cause Oracle to use only one of the available paths, leading to potential issues if that path fails. This article discusses the configuration of the oracleasm.conf file and highlights the importance of parameters like SCANORDER and SCANEXCLUDE to prevent such problems.
Key Parameters
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ORACLEASM_SCANORDER
- This parameter determines the order in which devices are scanned. In a multipath setup, you want Oracle ASM to prioritize scanning the multipath devices (usually named
dm-*ormpath*) over the individual paths (e.g.,sda,sdb). -
Example:
ORACLEASM_SCANORDER="dm" - This setting ensures that Oracle ASM will prioritize the multipath devices during its device scan, preventing the use of a single path.
- This parameter determines the order in which devices are scanned. In a multipath setup, you want Oracle ASM to prioritize scanning the multipath devices (usually named
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ORACLEASM_SCANEXCLUDE
- This parameter specifies which devices should be excluded from the ASM scan. For instance, if you have a multipath configuration, you should exclude the individual paths to ensure that only the multipath devices are used.
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Example:
ORACLEASM_SCANEXCLUDE="sd" - By excluding individual paths like
sd*, you reduce the risk of Oracle using an unintended single path instead of the multipath device.
Potential Issues with Incorrect Configuration
If the SCANORDER and SCANEXCLUDE parameters are not correctly configured, Oracle might only use one of the available paths, which could lead to significant problems if that path becomes unavailable. This could cause the database to crash or become inaccessible, particularly in environments where high availability is critical.
For example, a colleague shared an experience where a failure to configure these parameters correctly led to Oracle relying on a single path instead of the multipath setup. When that path failed, the database experienced downtime. Proper configuration of these parameters can prevent such issues and ensure that Oracle ASM fully utilizes the multipath capabilities of the storage environment.
Conclusion
Proper configuration of oracleasm.conf is crucial in environments where Oracle ASM and multipath are used together. By correctly setting parameters like SCANORDER and SCANEXCLUDE, you can ensure that Oracle ASM efficiently utilizes all available paths and avoids relying on a single path, reducing the risk of downtime and improving overall system reliability.