Gluster users - Nov 2016 - [Gluster-devel] Feedback on DHT option "cluster.readdir-optimize"

On Thu, Nov 10, 2016 at 3:17 AM, Nithya Balachandran
<nbalacha at redhat.com> wrote:
>
>
> On 8 November 2016 at 20:21, Kyle Johnson <kjohnson at gnulnx.net>
wrote:
>>
>> Hey there,
>>
>> We have a number of processes which daily walk our entire directory
tree
>> and perform operations on the found files.
>>
>> Pre-gluster, this processes was able to complete within 24 hours of
>> starting.  After outgrowing that single server and moving to a gluster
setup
>> (two bricks, two servers, distribute, 10gig uplink), the processes
became
>> unusable.
>>
>> After turning this option on, we were back to normal run times, with
the
>> process completing within 24 hours.
>>
>> Our data is heavy nested in a large number of subfolders under
/media/ftp.
>
>
> Thanks for getting back to us - this is very good information. Can you
> provide a few more details?
>
> How deep is your directory tree and roughly how many directories do you
have
> at each level?
> Are all your files in the lowest level dirs or do they exist on several
> levels?
> Would you be willing to provide the gluster volume info output for this
> volume?
>>

I have had performance improvement with this option when the first
level below the root consisted several thousands of directories
without any files. IIRC, I was testing this in a 16 x 2 setup.

Regards,
Vijay

On Thu, Nov 10, 2016 at 8:57 PM, Vijay Bellur <vbellur at redhat.com>
wrote:
> On Thu, Nov 10, 2016 at 3:17 AM, Nithya Balachandran
> <nbalacha at redhat.com> wrote:
> >
> >
> > On 8 November 2016 at 20:21, Kyle Johnson <kjohnson at
gnulnx.net> wrote:
> >>
> >> Hey there,
> >>
> >> We have a number of processes which daily walk our entire
directory tree
> >> and perform operations on the found files.
> >>
> >> Pre-gluster, this processes was able to complete within 24 hours
of
> >> starting.  After outgrowing that single server and moving to a
gluster
> setup
> >> (two bricks, two servers, distribute, 10gig uplink), the processes
> became
> >> unusable.
> >>
> >> After turning this option on, we were back to normal run times,
with the
> >> process completing within 24 hours.
> >>
> >> Our data is heavy nested in a large number of subfolders under
> /media/ftp.
> >
> >
> > Thanks for getting back to us - this is very good information. Can you
> > provide a few more details?
> >
> > How deep is your directory tree and roughly how many directories do
you
> have
> > at each level?
> > Are all your files in the lowest level dirs or do they exist on
several
> > levels?
> > Would you be willing to provide the gluster volume info output for
this
> > volume?
> >>
>
>
> I have had performance improvement with this option when the first
> level below the root consisted several thousands of directories
> without any files. IIRC, I was testing this in a 16 x 2 setup.
>
Yes Vijay. I remember you mentioning it. This option is expected to only
boost readdir performance on a directory containing subdirectories. For
files it has no effect.

On a similar note, I think we can also skip linkto files in readdirp  (on
brick) as dht_readdirp picks the dentry from subvol containing data-file.

> Regards,
> Vijay
> _______________________________________________
> Gluster-devel mailing list
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>


-- 
Raghavendra G
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