[gpfsug-discuss] GPFS 4.2 / Protocol nodes

[Oesterlin, Robert]

My experience is that in small clusters, it’s acceptable to double up on some of these services, but as you scale up, breaking them out makes more sense. Spectrum Scale make it easy to add/remove the nodes non-disruptively, so you can move them to dedicated nodes. When I first started testing 4.2, I setup a 6 node cluster that had both NSD and CES on them, and it did just fine. The nodes were 4-core 32GB and I had NFS and Object running on the CES nodes. The new CES nodes run a ton more services, especially when you start working with Object.

Both of you points are valid considerations – especially with CNFS. I’m running multiple CNFS clusters and having them broken out has save me a number of times.

Bob Oesterlin
Sr Storage Engineer, Nuance HPC Grid



From: <gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>> on behalf of Daniel Kidger <daniel.kidger at uk.ibm.com<mailto:daniel.kidger at uk.ibm.com>>
Reply-To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Date: Monday, January 11, 2016 at 8:42 AM
To: "gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>" <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Cc: "gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>" <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Subject: Re: [gpfsug-discuss] GPFS 4.2 / Protocol nodes

It looks like no one has attempted to answer this, so I will step in to start the conversation.

There are two issues when considering how many services to run on the same nodes - in this case the NSD servers.

1. Performance.
Spectrum Scale's (nee GPFS) core differentiator is performance. The more you run on a node the more that node resource's have to be shared. Here memory bandwidth and memory space are the main ones. CPU may also be a limited resource although with modern chips this is less likely so.
If performance is not the key delivered metric then running other things on the NSD server may be a good option so save both cost and server spawl in small datacentres.

2. NFS server stability.
pre-4.1.1, IBM used cNFS to provide multiple NFS servers in a GPFS cluster. This used traditional kernel based NFS daemons. If one hung then the whole node had to be rebooted which might have led to disruption in NSD serving if the other NSD server of a pair was already under load. With 4.1.1 came Cluster Export Services (CES) deliverd from 'Protocol Nodes'. Since there use Ganesha there would be no need to reboot this node if the NFS serving hung and in Ganesha, all NFS activity is in userspace not the kernel.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://gpfsug.org/pipermail/gpfsug-discuss_gpfsug.org/attachments/20160112/ffe59582/attachment.htm>