Thanks Ravi. That was my understanding - that the opening of the file is checked for health with all nodes, and then the file is actually read from one node. I think it's clear that checking with all nodes when opening the file for a read can't be avoided at the moment.
On Tue, 10 Aug 2021 at 22:32, Ravishankar N <ranaraya@xxxxxxxxxx> wrote:
On Tue, Aug 10, 2021 at 3:23 PM David Cunningham <dcunningham@xxxxxxxxxxxxx> wrote:Thanks Ravi, so if I understand correctly latency to all the nodes remains an issue on all file reads.Hi David, yes, but only for the lookup and opening of the fd. Once the fd is open, all readv calls will go only to the chosen brick.-RaviOn Tue, 10 Aug 2021 at 16:49, Ravishankar N <ranaraya@xxxxxxxxxx> wrote:On Tue, Aug 10, 2021 at 8:07 AM David Cunningham <dcunningham@xxxxxxxxxxxxx> wrote:Hi Gionatan,Thanks for that reply. Under normal circumstances there would be nothing that needs to be healed, but how can local-node know this is really the case without checking the other nodes?If using local-node tells GlusterFS not to check other nodes for the health of the file at all then this sounds exactly like what we're looking for, although only for a GlusterFS node that is also a client. My understanding is that local-node isn't applicable to a machine that only has the client.Does anyone know definitively what is the case here? If not I guess we would need to test it.Knowledge about the file's health is maintained in-memory by AFR xlator on each gluster client (irrespective of where it is mounted). This info is computed during lookup (lookups are always sent to all replica copies) which is issued before any data operation (read, write, etc). See https://docs.gluster.org/en/latest/Administrator-Guide/Automatic-File-Replication/#read-transactions.Regards,RaviThank you.On Thu, 5 Aug 2021 at 07:28, Gionatan Danti <g.danti@xxxxxxxxxx> wrote:Il 2021-08-03 19:51 Strahil Nikolov ha scritto:
> The difference between thin and usual arbiter is that the thin arbiter
> takes in action only when it's needed (one of the data bricks is down)
> , so the thin arbiter's lattency won't affect you as long as both data
> bricks are running.
>
> Keep in mind that thin arbiter is less used. For example, I have never
> deployed a thin arbiter.
Maybe I am horribly wrong, but local-node reads should *not* involve
other nodes in any manner - ie: no checksum or voting is done for read.
AFR hashing should spread different files to different nodes when doing
striping, but for mirroring any node should have a valid copy of the
requested data.
So when using choose-local all reads which can really be local (ie: the
requested file is available) should not suffer from remote party
latency.
Is that correct?
Thanks.
--
Danti Gionatan
Supporto Tecnico
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--David Cunningham, Voisonics Limited
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--David Cunningham, Voisonics Limited
http://voisonics.com/
USA: +1 213 221 1092
New Zealand: +64 (0)28 2558 3782
--
David Cunningham, Voisonics Limited
http://voisonics.com/
USA: +1 213 221 1092
New Zealand: +64 (0)28 2558 3782
http://voisonics.com/
USA: +1 213 221 1092
New Zealand: +64 (0)28 2558 3782
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