During an intra-series upgrade from //XR3 to //XR4, which command should the Implementation Engineer run...

In a Non-Disruptive Upgrade (NDU), ensuring that the host is correctly multipathed and balancing I/O across all paths is critical before taking a controller down. If a host is only using paths to the controller about to be rebooted (CT0, for example), taking that controller offline would cause an outage.

The commandiobalance --sampletime 30(or its wrapper purehost monitor --balance) is the standard tool used during the upgrade procedure to validate this state.

iobalance: This script samples the I/O throughput on all ports for a specified duration (e.g., 30 seconds).

It analyzes the distribution of I/O. If it detects that I/O is heavily skewed or missing entirely on the "secondary" paths (the ones that will survive the reboot), it flags a warning.

This allows the Implementation Engineer to pause and remediate the host multipathing configuration (e.g., fixing a bad cable or zoning issue) before proceeding with the controller removal, ensuring the NDU remains truly non-disruptive.