[Gluster-users] MTU size issue?

[Atin Mukherjee]

On 10/14/2015 05:09 PM, Sander Zijlstra wrote:
> LS,
> 
> I recently reconfigured one of my gluster nodes and forgot to update the MTU size on the switch while I did configure the host with jumbo frames.
> 
> The result was that the complete cluster had communication issues.
> 
> All systems are part of a distributed striped volume with a replica size of 2 but still the cluster was completely unusable until I updated the switch port to accept jumbo frames rather than to discard them.
This is expected. When enabling the network components to communicate
with TCP jumbo frames in a Gluster Trusted Storage Pool, you'd need to
ensure that all the network components such as switches, nodes are
configured properly. I think with this setting you'd fail to ping the
other nodes in the pool. So that could be a step of verification before
you set the cluster up.
> 
> The symptoms were:
> 
> - Gluster clients had a very hard time reading the volume information and thus couldn’t do any filesystem ops on them.
> - The glusterfs servers could see each other (peer status) and a volume info command was ok, but a volume status command would not return or would return a “staging failed” error.
> 
> I know MTU size mixing and don’t fragment bit’s can screw up a lot but why wasn’t that gluster peer just discarded from the cluster so that not all clients kept on communicating with it and causing all sorts of errors.
To answer this question, peer status & volume info are local operation
and doesn't incur N/W, so in this very same case you might see peer
status showing all the nodes are connected all though there is a
breakage, OTOH in status command originator node communicates with other
peers and hence it fails there.

HTH,
Atin
> 
> I use glusterFS 3.6.2 at the moment…..
> 
> Kind regards
> Sander
> 
> 
> 
> 
> 
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