Multipathing is a software solution that is implemented at the host-operating-system level. While multipathing is optional, it provides path redundancy, failover, and performance-enhancing capabilities. We recommend deploying the solution in any environment where availability and performance are critical.
The following list includes the main benefits of using an MPIO solution:
- Increase database availability by providing automatic path failover and failback.
- Enhance database I/O performance by providing automatic load balancing and capabilities for multiple parallel I/O paths.
- Ease administration by providing persistent, intuitive names for the storage devices across cluster nodes.
Multipath software solutions
The native Linux multipath solution is supported and bundled with most popular Linux distributions in use today. Because the software is widely and readily available at no additional cost, many administrators prefer it to other third-party solutions.
Only one multipath software solution should be enabled on the host.
Connectivity guidelines
The following list provides a summary of array-to-host connectivity best practices:
- Have at least two FC/iSCSI HBAs or ports to provide path redundancy.
- Connect the same port on both PowerStore nodes to the same switch. PowerStore matches the physical port assignment on both nodes.
- Use multiple switches to provide switch redundancy.
For more information, see the following documents:
Configuration file
To simplify deployment, the native Linux multipath software comes with default settings for an extensive list of storage models from different vendors including PowerStore. The default settings allow the software to work with PowerStore immediately. However, these settings might not be optimal for all situations and should be reviewed and modified if necessary.
The multipath daemon configuration file must be created on newly installed systems. A basic template can be copied from /usr/share/doc/device-mapper-multipath-<version>/multipath.conf to /etc/multipath.conf as a starting point. Any settings that are not defined explicitly in /etc/multipath.conf would assume the default values. The full list of settings (explicitly set and default values) can be obtained using the following command. The default settings generally work without any issues.
# multipathd –k"show config"
For more information, see www.dell.com/powerstoredocs and the document Dell PowerStore: Clustering and High Availability.
Creating device-mapper aliases
For ease of management, assign meaningful names (aliases) to the multipath devices. For example, create aliases that are based on the application type and environment that the device is in. The following snippet assigns an alias of esdata to the PowerStore LUN with WWN 368ccf09800f1fc382938798ae1a00ad2.
multipaths {
multipath {
wwid "368ccf09800f1fc382938798ae1a00ad2"
alias esdata
}
}
For more information, see www.dell.com/powerstoredocs and the document Dell PowerStore: Clustering and High Availability.
Asymmetric Logic Unit Access
PowerStore supports Asymmetric Logic Unit Access (ALUA) for host access. This feature allows the host operating system to differentiate between optimized paths and nonoptimized paths.
