A storage administrator has created a VPLEX distributed device.

When a VPLEX distributed device experiences elongated write response times, it is typically due to the characteristic of VPLEX that requires writes to be committed to backend storage on both clusters before an acknowledgement is sent to the host. This ensures data integrity and consistency across the distributed device but can lead to increased response times, especially if there is network congestion or latency issues between the clusters.

Here’s a detailed explanation:

Write I/O Commitment:For a VPLEX distributed device, any write I/O must be committed to backend (BE) storage on both the local and remote clusters1.

Network Impact:If the inter-cluster communication network (FC/IP WAN) is experiencing congestion or high latency, it will increase the round-trip time of I/O packets, leading to performance issues and elongated write response times1.

Performance Best Practices:VPLEX best practices suggest that the round-trip time (RTT) between clusters should not exceed 5 ms to maintain optimal performance, with an RTT of 1 ms recommended for campus-wide networks1.

Troubleshooting Steps:To address such issues, administrators should check for network congestion indicators in the firmware logs and ensure that all WAN communication ports are operational and that SFPs have sufficient power1.

Resolution:If the VPLEX is configured for FC metro and supported by Dell EMC, collecting switch logs and engaging Dell EMC support is advised.For IP metro configurations, validating the health of the IP network is crucial to identify the cause of congestion1.

By understanding this characteristic of VPLEX distributed devices, storage administrators can take appropriate measures to mitigate elongated write response times and maintain system performance.