I have a Hyper-V setup where guest OS'es accesses the host/parent OS via an Internal Network. I've noticed that "Microsoft Virtual Machine Bus Network Adapter" has support for Jumbo Packets and disabled by default. Does enabling this setting, both on host and the guests, makes any performance boost of network activity? Thanks!
Enabling Jumbo Packet support on Hyper-V internal network NIC
hyper-vhyper-v-server-2008-r2jumboframesnetworkingperformance
Best Answer
It depends greatly on the kind of I/O you're doing. It works great for iSCSI and FCoE because those protocols rely on a data frame size larger than the standard 1500b MTU for Ethernet. For regular old file transfers, the improvement isn't always apparent. And for databasy stuff that tends to be smaller than 1500b anyway, it doesn't do a thing. It's generally kept off by default because it minimizes things that can go wrong.
Where jumbo packets really do help is that it allows the TCP conversation to start at a higher base throughput when dealing with larger transfers. No need to negotiate window size, when what you're passing can fit in a 4Kb packet.