Issues with Jumbo frames on non-Intel cards

[mackwage]

Has anyone had issues with jumbo frames on non-Intel cards? Specifically, Realtek cards? (Realtek® 8111F here)

I swapped mobos for my system today and reinstalled freenas. When I set the mtu to 9000 now, I get quirky behavior. When I browse to the CIFS share and try to copy a file from the share to my local desktop, it will copy for 1 second then speed drops to 0mb. I tried this from 3 different pcs.

While this happens, no system can ping freenas and the mgmt internet is not accessible. It returns in about 60-90 seconds.

I am currently putting two dedicated Intel NICs in to to see if it resolves the issue. But want to see if it could possibly be anything I am overlooking.

Everything on the network side is fine.. jumbo frames enabled on my switch and workstations.

 

[joeschmuck]

I don't want your question to go unanswered but you may need to find a Realtek support group for this type of question, or maybe look into a FreeBSD forum. My advice is to drop the jumbo frames to a smaller value and to be honest, I doubt you will get much more throughput with jumbo frames turned on under real world use but I guess it depends on what you are using FreeNAS for.

 

[cyberjock]

Realteks = fail

jumbo frames = fail(normally)

So naturally.. I'd think "realtek + jumbo frames = double fail".

Ok, so there's no such thing as a double fail, but I wouldn't even consider trying it...

 

[mackwage]

No no no. I think double fail is definitely warranted in this situation. :)

Does FreeNas really not play well with Jumbo Frames? I am hosting VMs from an NFS mount. With most other storage vendors, (Dell, NetApp, Nimble), it is best practice and pretty well required to serve up your VMs with jumbo enabled.

 

[cyberjock]

FreeNAS plays fine with Jumbo Frames. The problem is that some manufacturers consider the frame to be part of the MTU and other's don't. If Intel considers it part of the frame(which I think is the spec), then the data packet will actually be the MTU. If you choose 9000 then it will be 9000 and never more. But, if you are with another brand(I'll use Realtek for this example but they may still do it properly, I don't know) they will not consider the fram to be part of the MTU. So their data packets are actually 9014 despite you setting it to 9000. When all of the talking devices don't support the same MTU everything goes to poop. So despite you thinking you set both correctly and all is right, you're getting boned by that Realtek.

Different brands do different things. Years ago I remember reading one company had 26 extra bytes. So jumbo frames *should* work but many brands just don't play right. IMO the easy surefire way to make sure that all of the cards work with the proper MTU is to use the same card for all of the devices. Not particularly cheap, but it worked for me.

Generally jumbo frames won't buy you much unless you are running 10Gb. So if you aren't trying to do 10Gb I wouldn't bother with jumbo frames.

Edit: Just for the record, I don't do jumbo frames at home.. too much hassle with making everything work. The only exception is my direct link from my server to my desktop. That is 10Gb, and that is jumbo frames.