I think you mean cluster.choose-local which is enabled by default. Yet, Gluster
will check if the local copy is healthy.
Best Regards,
Strahil Nikolov
? ?????, 28 ??? 2021 ?., 10:20:55 ?. ???????+3, Yaniv Kaul <ykaul at
redhat.com> ??????:
On Wed, Jul 28, 2021 at 5:50 AM David Cunningham <dcunningham at
voisonics.com> wrote:> Hi Yaniv,
>
> It may be my lack of knowledge, but I can't see how the fastest
response time could differ from file to file. If that's true then it would
be enough to only periodically test which node is fastest for this client, not
having to do it for every single read.
In real life, the 'best' node is the one with the highest overall free
resources, across CPU, network and disk IO. So it could change and it might
change all the time.
Network, disk saturation might be common, disk performing garbage collection,
CPU being hogged by something, noisy neighbor, etc...
Our latency check is indeed not per file, AFAIK.
Y.
>
> Thanks for the tip about read-hash-mode. I see the help is as below. Value
4 may help, but not if the latency is tested for every file read. Value 0 may
help, but it depends how the children are ordered. Does anyone know more about
how these work?
>
> Option: cluster.read-hash-mode
> Default Value: 1
> Description: inode-read fops happen only on one of the bricks in replicate.
AFR will prefer the one computed using the method specified using this option.
> 0 = first readable child of AFR, starting from 1st child.
> 1 = hash by GFID of file (all clients use same subvolume).
> 2 = hash by GFID of file and client PID.
> 3 = brick having the least outstanding read requests.
> 4 = brick having the least network ping latency.
>
> Thanks again.
>
>
> On Tue, 27 Jul 2021 at 19:16, Yaniv Kaul <ykaul at redhat.com> wrote:
>>
>>
>> On Tue, Jul 27, 2021 at 9:50 AM David Cunningham <dcunningham at
voisonics.com> wrote:
>>> Hello,
>>>
>>> We have a replicated GlusterFS cluster, and my understanding is
that the GlusterFS FUSE client will check the file with all nodes before doing a
read.
>>>
>>> For our application it is not actually critical to be certain of
having the latest version of a file, and it would be preferable to speed up the
read by simply reading the file from the fastest node. This would be especially
beneficial if some of the other nodes have higher latency from the client.
>>
>> How do you define, in real time, per file, which is the fastest?node?
>> Maybe you are looking for read-hash-mode volume option?
>> Y.
>>
>>>
>>> Is it possible to do this? Thanks in advance for any assistance.
>>>
>>> --
>>> David Cunningham, Voisonics Limited
>>> http://voisonics.com/
>>> USA: +1 213 221 1092
>>> New Zealand: +64 (0)28 2558 3782
>>> ________
>>>
>>>
>>>
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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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