Understanding MTU: The Maximum Transmission Unit (MTU) defines the largest size of a packet or frame that can be sent in a single network transaction. The standard Ethernet MTU is 1500 bytes. Anything larger than 1500 bytes is referred to as a Jumbo Frame.
Replication Efficiency: Replication involves moving large amounts of data between arrays. Using standard 1500-byte frames results in higher overhead because the CPU must process a larger number of headers for the same amount of data. By increasing the MTU, the FlashArray can pack more data into each frame, reducing CPU interrupts and improving overall throughput.
The Pure Recommendation: Pure Storage specifically recommends an MTU of 9000 for both iSCSI and Replication traffic. This is the industry standard for Jumbo Frames that balances efficiency with compatibility across most enterprise-grade switches.
Configuration Requirements: It is critical to remember that MTU must be configured end-to-end. For an MTU of 9000 to work on the replication ports:
The FlashArray replication ports must be set to 9000.
The network switches along the path (and any routers/ISLs) must support and be configured for at least 9000.
The target array's replication ports must also be set to 9000.
Why 9216 (Option A) is incorrect: While some switches support a "Baby Giant" or slightly larger MTU like 9216 to account for VLAN tagging overhead, Pure's internal and best practice documentation specifically points to 9000 as the standard setting for the array's interface.