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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!

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AND ALSO: Is there any possibility of data corruption/loss if the software doesn't expect that large packet size for network transfers? –  huseyint Feb 3 '11 at 19:18

2 Answers 2

up vote 4 down vote accepted

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.

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The type of I/O I'm doing in this case is database (MS SQL Server) and file transfer over a Windows share. –  huseyint Feb 3 '11 at 19:14
    
In that case, the database isn't likely to notice any difference in performance. The file transfers might, but it depends on how large the files are. –  sysadmin1138 Feb 3 '11 at 19:20
    
I enabled 9K jumbo frames on a Hyper-V host's virtual adapter and now I cannot RDP into it. Hmmn. –  paradroid Mar 25 '12 at 15:48

It would increase your network performance, if everything on your network is configured for it and your switches can handle it. It's mostly used if you're running iSCSI.

Good explanation: http://blog.allanglesit.com/Blog/tabid/66/EntryId/55/Enabling-Jumbo-Frames-on-Hyper-V-2008-R2-Virtual-Switches.aspx

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