Re: [Postgres-xc-general] newbie - testing and initial setup

[Attila B. <att...@se...>]

Hi,

Thanks for the lightning fast reply.
>>
>> 2. Postgres-XC
>> The overall structure of the replication looks pretty convincing but 
>> I have a few question:
>> - I read somewhere/saw in a slide deck (unfortunately I cannot find 
>> it any more) that it creates a performance bottleneck to have the 
>> coordinator and the datanode on the same machine (VMs in my test 
>> case). Is it still valid?
>
> No it is not valid.   Instead, for simpler load balancing between 
> coordinator and datanode, we advice to configure both on the same 
> machine.   This can also utilize data localization for better performance.

That is good to know.

>> - Is it possible to add 'slave' datanodes to the DB cluster, e.g an 
>> external web server?
>
> Yes.   pgxc_ctl from contrib module will help much.   You will find 
> the reference at 
> http://postgres-xc.sourceforge.net/docs/1_2_1/pgxc-ctl.html
>
> You will find sample configuration and pgxc_ctl demo scenario from 
> https://sourceforge.net/apps/mediawiki/postgres-xc/index.php?title=PGOpen2013_Postgres_Open_2013

I will definitely check it out.

>> - Approximate overhead/latency? I guess if the user connects to the 
>> local (i.e. the user's office) coordinator and commits some changes, 
>> the user still have to wait for the data to be sync'd with all the 
>> datanodes in the cluster, right? What if the DB cluser includes 
>> coordinators/datanodes from all over the globe?
>
> We’ve not assumed the usecase where coordinators/datanodes are 
> geometrically distributed, not because of the latency but to provide 
> full-featured transaction ACID capability over the cluster.     In the 
> local configuration, this latency is ignorable.

I'll test this anyway; I am kind of curious what will be the performance 
like.

Cheers,
Attila