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  • Latest Post - ‏2013-05-02T18:44:41Z by esj
5 Posts

Pinned topic adding placeholder NSD server entries to server list in advance of expansion?

‏2013-04-29T13:25:22Z |

The requirement that filesystems must be brought down to add NSD servers or change the order of the server list is very disruptive.

We need to have a maintenance outage very soon to change the order of our existing NSD servers. We will also be expanding our GPFS servers in the near future (~3 months). I wanted to get opinions on adding placeholder entries for these new machines to the server list for each NSD now, even though the machines (and DNS records, etc.) do not yet exist.

For example, the mmchnsd stanza might look like:


The goal is to avoid future filesystem outages for the NSD change when the machines are installed.

I'd like to know:

  • Will GPFS let me add a hostname to the server list if that host has not yet been added as a GPFS node?
  • How will the absence of the machines affect performance (ie., will there be noticable timeouts if the first "N" hosts in the NSD server list do not exist)?
  • Are there other downsides to preparing the filesystem in this way?
  • esj
    104 Posts

    Re: adding placeholder NSD server entries to server list in advance of expansion?


    You can specify as NSD servers only nodes that are legitimate members of the cluster.

    The main GPFS daemon (the mmfsd process) does not have to be up but otherwise the nodes

    must be reachable via ssh (or whatever your remote shell command is) and the nodes must

    have access to the disks that they are going to serve.  Changing these requirements is not trivial

    and will require major rework of the code.  This cannot be bypassed lightly.