[Gluster-users] Read from fastest node only

[Ravishankar N]

On Tue, Aug 10, 2021 at 3:23 PM David Cunningham <dcunningham at voisonics.com>
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.
-Ravi


>
> On Tue, 10 Aug 2021 at 16:49, Ravishankar N <ranaraya at redhat.com> wrote:
>
>>
>>
>> On Tue, Aug 10, 2021 at 8:07 AM David Cunningham <
>> dcunningham at voisonics.com> 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,
>> Ravi
>>
>>
>>> Thank you.
>>>
>>> On Thu, 5 Aug 2021 at 07:28, Gionatan Danti <g.danti at assyoma.it> 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
>>>> Assyoma S.r.l. - www.assyoma.it
>>>> email: g.danti at assyoma.it - info at assyoma.it
>>>> GPG public key ID: FF5F32A8
>>>>
>>>
>>>
>>> --
>>> 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
>
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