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I am having problems getting Jumbo Frames working over my iSCSI connection.

Here is what I try.

  • 4 1GbE connections on 4 different subnets on my NAS4Free array for iSCSI, MTU set at 9000
  • 2 redunant switches with the MTU set at their maximum 12288(or something like that)
  • 1 vSwitch MTU 9000
  • 4 vNICs MTU 9000

If I turn the vNICs MTU from 1500 to 9000 everything stops working, I can't even turn on or off a VM on the associated datastore.

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3
  • Do you need Jumbo frames?
    – ewwhite
    Jul 26, 2014 at 23:01
  • From what I had researched if I can turn it on it is beneficial to do so. And I have a SAN unti from Dell that appears to support Jumbo Frames and only Jumbo Frames.
    – Litzner
    Jul 26, 2014 at 23:07
  • 1
    @ewwhite They generally make sense on something like ISCSI - the overhead and packet reduction can seriously take load of the network in this particular case.
    – TomTom
    Jul 28, 2014 at 10:04

1 Answer 1

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I have punted for this array, the problem I am having seems to be pointing back at the NAS4Free array, since I can use 9000 MTU for VMotion just fine (over the same NICs and switches, just different vNICs). I am going to create two iSCSI storage networks, one that operates as 1500 MTU and one that operates at 9000 MTU. When I transition my other SAN units to the cluster I will attempt to get them working on the Jumbo Frame network.

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