Changing the Maximum Transmission Unit (MTU) from the default of 1500 bytes to a larger value, such as 9000 bytes (known as Jumbo Frames), significantly increases iSCSI throughput. A larger MTU allows more data to be sent in a single network packet. This reduces the total number of packets and headers that need to be processed for a given amount of data, which lowers the CPU overhead on both the host and the E-Series storage system. The result is more efficient data transfer and higher overall throughput. For this change to be effective, the MTU must be increased consistently across the entire data path, including the host, network switches, and the storage controller ports.

B. flow control: Flow control is a mechanism to prevent packet loss due to buffer overruns, not a setting to increase throughput. Improper configuration can actually hinder performance.

C. Challenge-Handshake Authentication Protocol (CHAP): CHAP is a security feature for authenticating iSCSI sessions. It adds negligible overhead during login and does not impact data transfer throughput.

D. Time to Live (TTL): TTL is an IP network parameter that prevents packets from looping indefinitely. It has no direct effect on the throughput of an established iSCSI connection.

1. NetApp Technical Report TR-4394

"NetApp E-Series with VMware vSphere 6.5 Best Practices

" Page 18

Section: iSCSI Network Configuration.

The document states

"For optimal performance

NetApp recommends enabling jumbo frames on all components in the iSCSI data path... Using jumbo frames reduces the processing overhead on the hosts and on the storage controllers

resulting in improved throughput."

2. NetApp E-Series SANtricam System Manager

"Configure iSCSI ports

" Online Documentation.

The documentation for configuring iSCSI ports explains the MTU setting: "The maximum transmission unit (MTU) is the size (in bytes) of the largest protocol data unit that a communication protocol can pass across the network. The default is 1500. You can change the value up to 9000 for jumbo frames

which can improve performance."

3. NetApp Technical Report TR-4569

"NetApp E-Series and EF-Series Best Practices for Microsoft SQL Server

" Page 20

Section: iSCSI Configuration.

This guide recommends

"Use jumbo frames (MTU 9000) for all iSCSI traffic. Jumbo frames improve performance by reducing the number of frames that must be sent and processed."