[gpfsug-discuss] AFM over NFS vs GPFS

[Luke Raimbach]

Anybody know the answer?

> HI All,
>
> We have two clusters and are using AFM between them to compartmentalise
> performance. We have the opportunity to run AFM over GPFS protocol (over IB
> verbs), which I would imagine gives much greater performance than trying to
> push it over NFS over Ethernet.
>
> We will have a whole raft of instrument ingest filesets in one storage cluster
> which are single-writer caches of the final destination in the analytics cluster.
> My slight concern with running this relationship over native GPFS is that if the
> analytics cluster goes offline (e.g. for maintenance, etc.), there is an entry in the
> manual which says:
>
> "In the case of caches based on native GPFS™ protocol, unavailability of the
> home file system on the cache cluster puts the caches into unmounted state.
> These caches never enter the disconnected state. For AFM filesets that use GPFS
> protocol to connect to the home cluster, if the remote mount becomes
> unresponsive due to issues at the home cluster not related to disconnection
> (such as a deadlock), operations that require remote mount access such as
> revalidation or reading un-cached contents also hang until remote mount
> becomes available again. One way to continue accessing all cached contents
> without disruption is to temporarily disable all the revalidation intervals until the
> home mount is accessible again."
>
> What I'm unsure of is whether this applies to single-writer caches as they
> (presumably) never do revalidation. We don't want instrument data capture to
> be interrupted on our ingest storage cluster if the analytics cluster goes away.
>
> Is anyone able to clear this up, please?
>
> Cheers,
> Luke.
>
> Luke Raimbach​
> Senior HPC Data and Storage Systems Engineer, The Francis Crick Institute, Gibbs
> Building,
> 215 Euston Road,
> London NW1 2BE.
>
> E: luke.raimbach at crick.ac.uk
> W: www.crick.ac.uk
>
> The Francis Crick Institute Limited is a registered charity in England and Wales
> no. 1140062 and a company registered in England and Wales no. 06885462, with
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