Re: [Postgres-xc-general] Performance when adding new datanode

[Mason S. <ma...@st...>]

On Mon, Sep 16, 2013 at 6:34 AM, Bartłomiej Wójcik <
bar...@tu...> wrote:

> Hello,
>
> Today I am testing the following simple cluster:    Host1(vm1, IP1,
> 6cores 4GB ram, disk storage(very large throughput  ~Gbit/s)):    1
> gtm    +    1 coordinator    +    (1,2,3) datanode
>
> Loading the database 100000 inserts and I received the time:       3m1s
> and    2m57s     (2 of 6 cores work mainly) -    100% of the data at
> each datanode (checked)
> Then I do simple selects on that data and I received the time:
> 28m29s  and  28m25s    (2 of 6 cores work mainly)
>
> I refresh the database (drop and create database)
> Then I add second datanode to the cluster, do the same test(inserts,
> selects) and I received:
>
> 2m59s    and  2m57s  (inserts)    (2 of 6 cores work mainly) - 50% of
> the data at each datanode (checked)
> 15m2s  and  13m41s  (selects)    (2 of 6 cores work mainly)
>
> I refresh the database (drop and create database again)
> Then I add third datanode and I received:
>
> 3m1s    and    2m58  (inserts)    (2 of 6 cores work mainly)    - 33% of
> the data at each datanode (checked)
> 9m35s  and  10m5s (selects)    (2 of 6 cores work mainly)
>
>
> Is this results ok ? Why did not increase write performance(inserts)
> after adding a datanode? Why did not benefit more from other cores ?
>
>
> The results are reproducible (as you can see)
>

How many clients/threads/processes did you have in the test? Just one? It
seems like it based on that not many cores were being used.

Was the test being run on the same server as the database?

Also, all of the "nodes" are sharing the same storage device, not dedicated
for each?

For a better test, you should use multiple clients and ideally multiple
servers, and preferably  dedicated storage.



>
>
> Regards!
>
> BW
>
>
>
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Regards,

-- 
Mason Sharp

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