Scenario:

In a large data center, the IT team received several complaints regarding high latency and slow application performance affecting end users. The data center relied on a Storage Area Network (SAN) for its storage infrastructure. The team needed to identify the root cause of the high latency and implement a solution to improve performance.

Background:

The data center used a Fibre Channel (FC) SAN to support various applications, including virtualized environments and database servers. The SAN infrastructure consisted of multiple storage arrays, Fibre Channel switches, and host bus adapters (HBAs) connecting the servers to the storage devices.

Actions:

1. Performance Monitoring:

The IT team started by monitoring the SAN’s performance using built-in tools and third-party applications to analyze I/O patterns, throughput, and latency. They observed an unusually high latency on specific storage arrays and identified a bottleneck.

2. Identifying Misconfigurations:

The team examined the configuration of the storage arrays, switches, and HBAs, focusing on zoning, LUN masking, and path selection policies. They discovered an issue with the multipathing configuration, causing an uneven distribution of traffic across the available paths, leading to congestion and high latency.

Configuration adjustments:

To resolve the multipathing issue, the IT team reconfigured the path selection policy on the affected servers:

a. On each server, they accessed the multipathing settings:

multipath -ll

b. They updated the path selection policy to ’round-robin’ for better load balancing:

# vi /etc/multipath.conf

defaults {
path_selector "round-robin 0"
}

c. They restarted the multipath daemon to apply the new configuration:

systemctl restart multipathd.service

3. Validating the Solution:

After implementing the changes, the IT team monitored the SAN performance and observed a significant reduction in latency and an improvement in I/O distribution across the available paths.

4. Documenting and Sharing:

The team documented the issue, solution, and configuration changes to ensure proper knowledge transfer and to prevent similar issues in the future.

Conclusion:

By identifying and addressing the root cause of high latency in the SAN, the IT team successfully improved the performance and user experience in the data center. This example highlights the importance of proper configuration and monitoring in maintaining optimal data center performance.