Using jumbo frames can improve iSCSI network bandwidth by up to 50 percent. When supported by the network, we recommend using jumbo frames to increase bandwidth.
Jumbo frames can contain more iSCSI commands and a larger iSCSI payload than normal frames without fragmenting or with less fragmenting depending on the payload size. On a standard Ethernet network the frame size is 1500 bytes. Jumbo frames allow packets configurable up to 9,000 bytes in length.
The VNX series supports 4,000, 4,080, or 4,470 MTUs for its front-end iSCSI ports. It is not recommended to set your storage network for Jumbo frames to be any larger then these.
If using jumbo frames, all switches and routers in the paths to the storage system must support and be capable of handling and configured for jumbo frames.
For example, if the host and the storage system’s iSCSI ports can handle 4,470-byte frames, but an intervening switch can only handle 4,000 bytes, then the host and the storage system’s ports should be set to 4,000 bytes.
Note that the File Data Mover has a different Jumbo frame MTU than the VNX front-end ports. The larger Data Mover frame setting should be used.