Topic
5 replies Latest Post - ‏2013-02-05T18:14:01Z by sdenham
VincenzoVagnoni
VincenzoVagnoni
94 Posts
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Pinned topic changing MTU without restarting GPFS

‏2013-02-04T17:00:47Z |
we want to switch to jumbo frames our client GPFS nodes. It looks like GPFS still uses mtu=1500 once the network device has been updated to mtu=9000. Is it necessary to restart GPFS for this to be digested? If yes, is there a way to circumvent a restart?
Updated on 2013-02-05T18:14:01Z at 2013-02-05T18:14:01Z by sdenham
  • dlmcnabb
    dlmcnabb
    993 Posts
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    Re: changing MTU without restarting GPFS

    ‏2013-02-04T18:34:35Z  in response to VincenzoVagnoni
    I don't think that the existing connections between nodes will change their MU settings in the kernel. New connections between nodes will probably get the new settings. If you look at the output of "mmfsadm dump tscomm" there will be stanzas for each connection. One set of stanzas will show the MTU setting being use by the operating system.
  • VincenzoVagnoni
    VincenzoVagnoni
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    Re: changing MTU without restarting GPFS

    ‏2013-02-04T20:06:12Z  in response to VincenzoVagnoni
    right. So there's no way to tell a GPFS node to re-establish all the connections without shutting down and dismounting.
    • sdenham
      sdenham
      70 Posts
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      Re: changing MTU without restarting GPFS

      ‏2013-02-04T23:24:34Z  in response to VincenzoVagnoni
      I believe this can be done without disturbing the GPFS clients, provided you have redundance in your NSD servers. When you shut down GFPS on an NSD server, the connections will be broken and requests will be serviced from an alternate NSD server. Then the connection is re-established when that NSD server is restarted. If you can cycle GPFS on all of your NSD servers one at a time, all of the connections will get re-established, and should pick up the new MTU size, as Dan suggested.
  • VincenzoVagnoni
    VincenzoVagnoni
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    Re: changing MTU without restarting GPFS

    ‏2013-02-05T09:14:10Z  in response to VincenzoVagnoni
    yes, this might work, although a bit painful and with some risk (150 servers)
    • sdenham
      sdenham
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      Re: changing MTU without restarting GPFS

      ‏2013-02-05T18:14:01Z  in response to VincenzoVagnoni
      150 NSD servers? Or 150 clients? You only need to do this on the NSD servers to re-establish all of the socket connections. If it's really 150 NSD servers.. yeah, that could take a while, but I've scripted this before to wait for mmgetstate to come back to active before moving on to the next server. And obviously with some forethought you can do more than one server at a time provided you don't cut all the paths to any single NSD at once.