HP NC7170 NIC card & Jumbo frames with AX4-5i

Hi,

The max MTU size on AX4-5 is 9000, you need to mach the 9000 of the clariion with the switch port.

Thanks

Madhusudan

Thanks Ganapa for the response.

The Switch is set at 9000, the AX4-5i is set at 9000.  The host server is at 1500.  When I change it to the 9014 (only choice the NIC driver gives for MTU besides the default), I get corrupt frames, and corrupt data.

So I guess I'm really asking, since teh NIC card frame choices are 9014 (rather than 9000), is that just a naming issue, or is it indeed 14 bytes larger than it is suppose to be?  And if it is, then I guess I am out of luck on using this card with Jumbo support?  And if that is the case, what is recommended by others around here for a good server NIC card?

Thanks,

James

Thanks Glen.  Definately a step into the right direction.  The HP docs are all but useless in talking about hte NIC properties.  I have no idea if I have it set to 9014, if that is "negotiable" upto that speed, or hard set so to speak.  When I set it earlier to that size over the weekend, everything coming off of the array with considered "corrupted".  I had to set it back and reboot the server to fix the issues.

I guess that also leads me to my second question, is there a recommended NIC card folks seem to like to use with these arrays?

Thanks,

James

Yea, did that. 1448 is all that it is curently passing.  I'll have to wait until maintenance window to set the server back to 9000 and see what is passing.

I did confirm that the switch was still set to Jumbo frame support, which per the HP switch docs will pass frames up to 9220.in size.  Not sure how to confirm that hte EMC is indeed already set to 9000 except, when I go to the menu on left side -> iSCSI -> A-0 (or any of the ports) It tells me the MTU of 9000.  Not completely sure that this is what it is set to, or the default choice to select the Apply against.

James

We have no recommendations on the brand of NIC's - most seem to work OK. If the host is set to 9014 and the array is set to 9000, it shoudl negotiate to 9000. If the switch is working, it should just pass the frames. Try running that ping test in emc151113  to see if the frames are getting through.

glen

Some switches can have the MTU set individually for each port. It's important each port associated with the host/array are all set the same.

Perform some ping tests the ensure that traffic is getting through consistently. The test consist of executing pings between the server and the array, varying the packet size (-l xxxx) with the non-fragmentable option (-f) set to determine the maximum MTU size that can be sent between the server and the array. Sizes that should be tried include: 1448, 1500 for small packet sizes and 4470, 5000, 7000, 8000, 8900, and 8972.

ping -t -f -l 8972 <IP address>

Note: MTU is the maximum amount of data in a frame, in this case an Ethernet frame not the maximum amount in an ICMP or TCP data. For a ping, an ICMP packet, you have to take into account the IP header and the ICMP header. There are 20 bytes and 8 bytes respectively. So 9000 - 20 - 8 = 8972 - this will be the maximum size that will work correctly when using ping - 8972.

On the AX4 - the default is 1500, so if you see 9000 in the MTU window that's what it's set for.

glen