Thanks for sharing the GC link Michel! 

Memory
Total heap (usage / alloc. max) 1,501.7M (81.7%) / 1,837.4M
Tenured heap (usage / alloc. max)       1,361.7M (80.7%) / 1,686.7M
Young heap (usage / alloc. max) 150.6M (100.0%) / 150.6M

I think the heap settings are not reflecting. Can you please try again? Please 
use -Xms and -Xmx both and set them to 8g. Also please try setting minimum 
young gen allocation to 2GB.
Can you also please mention what tests are you comparing? 

Regards
Lokesh

> On 30-Jul-2020, at 8:33 PM, Michel Sumbul <michelsum...@gmail.com> wrote:
> 
> Hi Lokesh,
> 
> Thanks for your advice.
> I changed the heap size from 3GB to 4Gb and then to 8GB, set to 
> dfs.ratis.client.request.retry to 10 and decreased the number of pipeline 
> from 5 to 2.
> It allows 10-15% better performance but it's still 35% slower than HDFS. I 
> also notice that the data is less well spread over the 4 nodes with only 2 
> pipelines.
> 
> I had a look at the GC log during the execution of the teragen (copy attach 
> this email), I'm not an expert at all in gc tuning so I load it the GC log on 
> this site and it tell me that for the 4 minutes of the execution of the job 
> the datanode was in pause during 29 seconds and trigger 1260 GC over 4 
> minutes. That looks pretty high for me but maybe not?
> http://gcloganalyzer.com/?file=70338453-4505-4238-a900-c0206a2d52f4test.gc  
> 
> I also take care that the yarn job don't request more than 80% of the VM 
> resource (even try with 60% but didn't change anything)
> 
> Do you think there is something else I can do to improve it or should I stop 
> here? Is it possible that the difference comes from the short circuit feature 
> of HDFS?
> 
> Thanks a lot,
> Michel
> 
> Le mer. 29 juil. 2020 à 10:54, Lokesh Jain <lj...@apache.org> a écrit :
> Hi Michel
> 
> Thanks for trying out Ozone! 
> For ozone 0.5 - Can you please try another run after increasing config value 
> for dfs.ratis.client.request.retry.interval to 10 or 15 seconds? The default 
> value for this config is 1 second.
> > ozone.datanode.pipeline.limit
> Can you try a smaller value like 1 or 2 for above config with a data node 
> heap size of 4GB? Please check GC pressure on the datanode with this config.
> 
> There are some improvements which have gone recently after ozone 0.5 release. 
> I would also recommend to try the latest ozone.
> 
> Thanks
> Lokesh
> 
> 
> > On 29-Jul-2020, at 12:57 AM, Michel Sumbul <michelsum...@gmail.com> wrote:
> > 
> > I forgot to mention that I set ozone.datanode.pipeline.limit to 5.
> > Michel
> > 
> > Le mar. 28 juil. 2020 à 20:22, Michel Sumbul <michelsum...@gmail.com 
> > <mailto:michelsum...@gmail.com>> a écrit :
> > Hi guys,
> > 
> > I would like to know if you have any advice tips/tricks to get the best 
> > performance of Ozone? (Memory tuning / thread / specific settings / etc..)
> > 
> > I did a few teragen/terasort on it and the results are really surprising 
> > compared to HDFS,Ozone (using the hadoopFS)  is almost 2 times slower than 
> > HDFS.
> > 
> > 
> > 
> > 
> > 
> > 
> > The clusters were exactly the same for both:
> > - 3 masters and 4 slaves (8core/32GB) (its a small cluster but that should 
> > matter here)
> > - Backend storage is a CEPH storage (80 servers)
> > - NIC: 2 x 25Gb/S
> > - Ozone version 0.5
> > - Each job was executed 5 times
> > 
> > HDFS and Ozone were installed on the same nodes, one was down where the 
> > other one was up, to guarantee no other differences of configuration that 
> > the distributed FS.
> > 
> > I was not expecting a big difference like this, do you have any idea how to 
> > improve this? 
> > Or what can be the reason for that? I saw a few jira regarding data 
> > locality at read, can it be linked to that?
> > 
> > Thanks,
> > Michel
> > 
> 
> 
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