To diagnose and resolve the intermittent performance and connection drop issues with the supplemental iSCSI storage, the administrator should focus on network layer consistency and health, particularly regarding packet size (MTU) and delivery (TCP).

Examine the iSCSI VMkernel port for TCP retransmissions (Action B - Diagnose):"Intermittent" connection drops and slow I/O are classic symptoms of packet loss or fragmentation issues. By examining the ESXi network stats (e.g., using esxtop key n or viewing vSphere performance charts) forTCP retransmissions, the administrator can confirm if packets are being dropped or lost in transit.Checksum offload errorscan also indicate issues where the NIC hardware is incorrectly validating packets, causing the OS to drop them. This step identifies theroot cause(packet loss/corruption).

Ensure all ESX hosts have the VMkernel port MTU set to 9000 (Action E - Resolve):For high-performance storage traffic like iSCSI in a VMware Cloud Foundation environment, it is best practice to useJumbo Frames (MTU 9000)end-to-end (Host -> Switch -> Storage Array).

The symptom thatsomehosts are affected suggestsconfiguration driftwhere those specific hosts might be set to a different MTU (e.g., 1500) or are mismatched with the physical network/target (which is likely set to 9000 for performance).

An MTU mismatch (e.g., Target sending 9000-byte frames to a Host/Switch expecting 1500) typically results in the "Do Not Fragment" (DF) bit causing packet drops, leading to the reported connection drops and retransmission delays. Ensuring a consistent MTU of 9000 across the fleet resolves this and aligns with VCF performance standards.

Note: Option A (CHAP) is for authentication security, not performance. Option C (Update network plugin) is a lifecycle task but less likely to be the immediate fix for "some hosts" having intermittent drops compared to the common issue of MTU mismatch. Option D (MTU 1500) would resolve drops if the physical network doesn't support Jumbo Frames, but would degrade performance, making E the preferred resolution for a "performance" storage tier.