[Gluster-users] Read from fastest node only

[David Cunningham]

Hi Strahil,

I registered and read the article, thank you. It looks like it would help
the speed of directory listing and related operations, but I don't see
anything to suggest that the other nodes won't be checked on file reads. Am
I missing something?

We would probably use something like 2 nodes nearby and 1 remote. I
understand that the thin arbiter keeps a track of which nodes are online,
but can't see how that will help with file reads and nodes being checked
for consistency. Are you able to explain please?

Thanks.



On Mon, 2 Aug 2021 at 17:45, Strahil Nikolov <hunter86_bg at yahoo.com> wrote:

> 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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> --
> David Cunningham, Voisonics Limited
> http://voisonics.com/
> USA: +1 213 221 1092
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>
>

-- 
David Cunningham, Voisonics Limited
http://voisonics.com/
USA: +1 213 221 1092
New Zealand: +64 (0)28 2558 3782
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