2 Replies Latest reply on Jan 31, 2013 6:51 PM by 988207

    Jumbo Frames issue ZFS 7120 + Dell PowerConnect Switch


      I am setting up an enviornment with a ZFS 7120 for iSCSI storage, connected to ESXi 5.1 host via a dedicated Dell PowerConnect 6224 switch.
      The 7120 has 2 ports dedicated to iSCSI, igb2 and igb1. These are in an LACP Aggregation with MTU of 9000 bytes. The PowerConnect docs recommend MTU on the ports of 9216 bytes. There is an EQuallogic SAN also connected to this switch (switch ports also at 9216 MTU, and jumbo frames enabled on equallogic side ... it all is working well).

      The ESXi 5.1 host has a vSwitch with MTU 9000, which also has 2 VMKernel ports with MTU 9000, and each has 1 dedicated vmnic for uplink to the Dell switch. In this configuration, I confirm that jumbo frames is OK by using vmkping -d -s 8972 <ipofsanarray> . I get response from Equallogic, indicating tha end-to-end jumbo frames is working. I get no response from the IP of the 7120, which means that there is some jumbo frame issue. I do a regular ping of the ZFS just fine, so the devices are connected and able to talk to each other. vmkping to regular servers connected (with Jumbo enabled) to the SAN works.

      It seems the issue is on the 7120 side of things (I think), but not sure where to start troubleshooting? Maybe I should break the LACP config?
        • 1. Re: Jumbo Frames issue ZFS 7120 + Dell PowerConnect Switch
          What's the output from "ifconfig -a" show on the 7120?

          Can you snoop the interface(s) from the 7120 and see if the packets are getting there? And if they are, are responses getting sent?

          Are all the other connections identical between the various storage devices? Same switch? Same switch port configs? If everything else is the same, yeah, I think I'd try simplifying things by dropping LACP and seeing if I could get it to work in a simpler configuration first.
          • 2. Re: Jumbo Frames issue ZFS 7120 + Dell PowerConnect Switch

            In the end, it turned out to be that the port-channel interface on the Dell did not have jumbo MTU set. I did the following to set it:

            interface port-channel 1
            mtu 9216
            copy run start

            At that point, both interfaces in the port channel got shutdown for some reason, the 7120 showed its 2 SAN interfaces as down too.

            So, I did a:

            no shutdown

            When the interfaces and port-channel came back up, I was able to vmkping -d -s 8972 to the target IP address, and from windows a ping -f -l 8972 worked. I am able to scan and see iSCSI targets now.

            Edited by: ziffsis on Jan 31, 2013 10:51 AM