[Gluster-users] Read from fastest node only

Strahil Nikolov hunter86_bg at yahoo.com
Mon Aug 2 05:45:30 UTC 2021

Hi David,
Can you register at developers.redhat.com and check the article about the md-cache. I think that for most cases the caching should be sufficient in order to not lookup the remote node.
By the way, are at least 2 of nodes nearby (lower lattency)? If only 1 node is 'remote' , then you can give a try to gluster's thin arbiter (for the 'remote' node).

Best Regards,Strahil Nikolov 
  On Mon, Aug 2, 2021 at 5:02, David Cunningham<dcunningham at voisonics.com> wrote:   Hi Ravi and Strahil,
Thanks again for your responses. Having one brick be the one to read (but with failover if that node goes completely offline) would be great if we could do it per client, but won't work if all clients have to use the same setting.
I'm not sure about gNFS, but normal NFS is something we've thought about as an option. I'm not sure if it will help though, because if the client NFS mounts the server which has the brick, then when it does a read presumably the brick will be checked for consistency with the other bricks and latency will be a problem again. If my understanding is correct even with choose-local enabled the other bricks will still be checked so the problem is not solved.
I confess that AFR vs eventual consistency is beyond my understanding of replication. In the world of SQL there is Galera cluster, and it will write to all nodes but for reads only checks the node the client is actually connected to. That's the sort of functionality we'd find really helpful for our use-case.

On Fri, 30 Jul 2021 at 19:21, Strahil Nikolov <hunter86_bg at yahoo.com> wrote:

Hi David,
md-cache will just save some lookup actions across the bricks, but it won't save you from all cases.
Using gNFS + cluster.choose-local is worth exploring, but as gNFS is deprecated I never checked if it will be affected by the lattency of the last brick.
What Ravi proposed looks promising, but it has some drawbacks - for example a brick dies and FUSE clienta have to be adjusted to read from another brick.
Ravi, I think that this topic was already discussed once.
Best Regards,Strahil Nikolov 
  On Fri, Jul 30, 2021 at 8:49, Ravishankar N<ranaraya at redhat.com> wrote:   ________

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