Any downside to Jumbo Frames??

One downside is that there is still a lot of gear out there that doesn't support Jumbo frames. Turning them on by default could make it hard to provision/setup the NAS. Also, since jumbo frames are not part of the ethernet standard, the size limit for jumbo frames varies (my laptop for instance is limited to 4088 bytes, other devices go to 9000).

I ran across this post in my googling... (a reply on http://www.codinghorror.com/blog/2009/0 ... rames.html)

I participated in the IEEE 802.3 committee for a while. IEEE never standardized a larger frame size for two reasons that I know of: 1. The end stations can negotiate the frame size, but there was no backwards-compatible way to ensure that all L2 bridges between them can handle it. Even if you send a jumbo frame successfully, you can still run into a problem later if the network topology changes and your packets begin taking a different path through the network. 2. The CRC32 at the end of the packet becomes weaker after around 4 KBytes of data. It can no longer guarantee that single bit errors will be caught, and the multibit error detection becomes weaker as well. One is free to enable it, and it does improve the performance, but the situation is unlikely to ever get better in terms of standard interoperability. It will always be an option to be enabled manually. Also a number of years ago,. jumbo frames provided a much bigger boost. Going from 1.5K to 9K regularly doubled performance or more. What has happened since is smarter ethernet NICs: they routinely coalesce interrupts, steer packets from the same flow to the same CPU, and sometimes even reassemble the payload of the 1.5K frames back into larger units. The resistance to standardizing jumbo frames resulted in increased innovation elsewhere to compensate.