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Round Robin path policy defines how to balance I/O load across active storage paths. In this best practice, the Round Robin path policy will be changed to optimize performance.
Category | PowerMax Storage |
Product | VMware ESXi |
Type of best practice | Performance Optimization |
Day and value | Day 1, Highly Recommended |
Overview
At the hypervisor layer, ESXi controls the flow of data to and from the server. There are several configuration choices including Most Recently Used (MRU), Fixed, and Round Robin. In this best practice, we made changes to the Round Robin path policy to optimize data path usage between the PowerEdge servers and the PowerMax storage.
Round Robin automatically rotates through all available paths to distribute the data flow. As PowerMax has all active paths to storage, Round Robin will rotate data across those pathways. By default, Round Robin sends 1,000 I/O operations across one path before using the next. In this best practice, we change the default of 1,000 I/O operations to 1. With a Round Robin IOPS limit of 1, the paths to storage rotate more frequently, improving overall performance, providing a positive impact upon storage performance.
Recommendation
Changing the Round Robin Path Policy to 1 showed a significant performance improvement in these performance metrics:
NOPM and TPM significantly increased when compared to the prior test, indicating the change to the Round Robin path policy improved performance.
An increase in PowerMax IOPS indicates more efficient use of I/O paths to storage. Optimal path usage benefits the database as the response times for reads and writes decrease.
Server processor utilization can be impacted by default settings that are not optimized. In this case, the default Round Robin setting of 1,000 I/O operations was impacting performance. Changing the Round Robin setting to 1 I/O before moving to the next path resulted in a more frequent path switch rate, which improved performance. An increase in server CPU use indicates less storage wait time and more efficient processor utilization.
PowerMax IOPS significantly increased, indicating that optimizing Round Robin multipathing enabled storage to process more I/Os per second. Both the PowerMax average read and write response times decreased. The combined increase in IOPS and decreases in response times means databases can process a greater volume of data faster.
Overall, the best practice of changing the Round Robin path policy from 1000 I/O operations to 1 is highly recommended and should be considered as a Day 1 practice as part of initial data provisioning.
Implementation Steps
To configure Round Robin, I/O operations from 1,000 (the default value) to 1, login into the ESXi console and run the following command (with the .xxxx in naa.xxxx matching the first few characters of your NAA ID):
for i in `esxcfg-scsidevs -c |awk '{print $1}' | grep naa.xxxx`; do esxcli storage nmp psp roundrobin deviceconfig set --type=iops --iops=1 --device=$i; done
Verify the change using the following command:
esxcli storage nmp device list
Additional Resources
This best practice was referenced from VMware Multipathing policies in ESXi/ESX and Adjusting Round Robin IOPS limit from 1000 to 1.