[gpfsug-discuss] data interface and management infercace.

Tue Jul 14 08:31:04 BST 2015

Hello Salvatore,

as you wrote that you have about 700 clients, maybe also the tuning recommendations for large GPFS clusters are helpful for you. They are on the developerworks GPFS wiki:

https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20%28GPFS%29/page/Best%20Practices%20Network%20Tuning

To my experience especially "failureDetectionTime" and "minMissedPingTimeout" may help in case of expelled nodes.

In case you use InfiniBand, for RDMA, there also is a "Best Practices RDMA Tuning" page:

https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20%28GPFS%29/page/Best%20Practices%20RDMA%20Tuning

Regards
Birgit

________________________________
From: gpfsug-discuss-bounces at gpfsug.org [gpfsug-discuss-bounces at gpfsug.org] on behalf of Salvatore Di Nardo [sdinardo at ebi.ac.uk]
Sent: Monday, July 13, 2015 3:29 PM
To: Vic Cornell
Cc: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] data interface and management infercace.

Hello Vic.
We are currently draining our gpfs to do all the recabling to add a management network, but looking what the admin interface does ( man mmchnode ) it says something different:

--admin-interface={hostname | ip_address}
                         Specifies the name of the node to be used by GPFS administration commands when communicating between nodes. The admin node name must be specified as an IP
                         address or a hostname that is resolved by the host command to the desired IP address.  If the keyword DEFAULT is specified, the admin  interface  for  the
                         node is set to be equal to the daemon interface for the node.

So, seems used only for commands propagation,  hence have nothing to do with the node-to-node traffic. Infact the other interface description is:

 --daemon-interface={hostname | ip_address}
                         Specifies the host name or IP address to be used by the GPFS daemons for node-to-node communication.  The host name or IP address must refer to the commu-
                         nication adapter over which the GPFS daemons communicate. Alias interfaces are not allowed. Use the original address or a name that  is  resolved  by  the
                         host command to that original address.

The "expired lease" issue and file locking mechanism a( most of our expells happens when 2 clients try to write in the same file) are exactly node-to node-comunication, so  im wondering what's the point to separate the "admin network".  I want to be sure to plan the right changes before we do a so massive task. We are talking about adding a new interface on 700 clients, so the recabling work its not small.

Regards,
Salvatore

On 13/07/15 14:00, Vic Cornell wrote:
Hi Salavatore,

Does your GSS have the facility for a 1GbE “management” network? If so I think that changing the “admin” node names of the cluster members to a set of IPs on the management network would give you the split that you need.

What about the clients? Can they also connect to a separate admin network?

Remember that if you are using multi-cluster all of the nodes in both networks must share the same admin network.

Kind Regards,

Vic

On 13 Jul 2015, at 13:31, Salvatore Di Nardo <sdinardo at ebi.ac.uk<mailto:sdinardo at ebi.ac.uk>> wrote:

Anyone?

On 10/07/15 11:07, Salvatore Di Nardo wrote:
Hello guys.
Quite a while ago i mentioned that we have a big  expel issue on our gss ( first gen) and white a lot people suggested that the root cause could be that we use the same interface for all the traffic, and that we should split the data network from the admin network. Finally we could plan a downtime and we are migrating the data out so, i can soon safelly play with the change, but looking what exactly i should to do i'm a bit puzzled. Our mmlscluster looks like this:

GPFS cluster information
========================
  GPFS cluster name:         GSS.ebi.ac.uk<http://GSS.ebi.ac.uk>
  GPFS cluster id:           17987981184946329605
  GPFS UID domain:           GSS.ebi.ac.uk<http://GSS.ebi.ac.uk>
  Remote shell command:      /usr/bin/ssh
  Remote file copy command:  /usr/bin/scp

GPFS cluster configuration servers:
-----------------------------------
  Primary server:    gss01a.ebi.ac.uk<http://gss01a.ebi.ac.uk>
  Secondary server:  gss02b.ebi.ac.uk<http://gss02b.ebi.ac.uk>

 Node  Daemon node name    IP address  Admin node name     Designation
-----------------------------------------------------------------------
   1   gss01a.ebi.ac.uk<http://gss01a.ebi.ac.uk>    10.7.28.2   gss01a.ebi.ac.uk<http://gss01a.ebi.ac.uk>    quorum-manager
   2   gss01b.ebi.ac.uk<http://gss01b.ebi.ac.uk>    10.7.28.3   gss01b.ebi.ac.uk<http://gss01b.ebi.ac.uk>    quorum-manager
   3   gss02a.ebi.ac.uk<http://gss02a.ebi.ac.uk>    10.7.28.67  gss02a.ebi.ac.uk<http://gss02a.ebi.ac.uk>    quorum-manager
   4   gss02b.ebi.ac.uk<http://gss02b.ebi.ac.uk>    10.7.28.66  gss02b.ebi.ac.uk<http://gss02b.ebi.ac.uk>    quorum-manager
   5   gss03a.ebi.ac.uk<http://gss03a.ebi.ac.uk>    10.7.28.34  gss03a.ebi.ac.uk<http://gss03a.ebi.ac.uk>    quorum-manager
   6   gss03b.ebi.ac.uk<http://gss03b.ebi.ac.uk>    10.7.28.35  gss03b.ebi.ac.uk<http://gss03b.ebi.ac.uk>    quorum-manager

It was my understanding that the "admin node" should use a different interface ( a 1g link copper should be fine), while the daemon node is where the data was passing , so should point to the bonded 10g interfaces.  but when i read the mmchnode man page i start to be quite confused. It says:

                   --daemon-interface={hostname | ip_address}
                         Specifies  the  host  name or IP address to be used by the GPFS daemons for node-to-node communication.  The host name or IP address must refer to the communication adapter over which the GPFS daemons communicate.
                         Alias interfaces are not allowed. Use the original address or a name that is resolved by the host command to that original address.

                   --admin-interface={hostname | ip_address}
                         Specifies the name of the node to be used by GPFS administration commands when communicating between nodes. The admin node name must be specified as an IP address or a hostname that is resolved by the  host command
                         to the desired IP address.  If the keyword DEFAULT is specified, the admin interface for the node is set to be equal to the daemon interface for the node.

What exactly means "node-to node-communications" ?
Means DATA or also the "lease renew", and the token communication between the clients to get/steal the locks to be able to manage concurrent write to thr same file?
Since we are getting expells ( especially when several clients contends the same file ) i assumed i have to split this type of packages from the data stream, but reading the documentation it looks to me that those internal comunication between nodes use the daemon-interface wich i suppose are used also for the data. so HOW exactly i can split them?

Thanks in advance,
Salvatore

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