Re: [Postgres-xc-general] Table distribution/replication and other things

On Wed, Jan 30, 2013 at 5:46 PM, Christophe Le Roux <
chr...@fr...> wrote:

>  Thank you for your answers.****
>
> ** **
>
> About the third question, I don’t want to use standby server for now
> (except for GM standby).****
>
> The cluster would be 4 servers :****
>
> ** **
>
> A – GTM server****
>
> B – GTM proxy, coordinator and datanode server****
>
> C – GTM proxy, coordinator and datanode server****
>
> D – GTM standby server****
>
> ** **
>
> All tables of all databases are “DISTRIBUTE by REPLICATION” (postgres-XC
> capability). So we have same data at the same time on datanodes B and C.**
> **
>
> So if B server fail , C server will do the job.****
>
> If C server fail, B server will do the job.****
>
> B and C server talk to A server (for GxId, sequence,..) but if A server
> fail, we can promote D server to the master GTM.****
>
> **
>

Thanks for elaborate example. Now it's clear. Here's a suggestion. You
don't need separate servers for GTM or GTM standby. They can share servers
with coordinator or datanode. But having them on separate servers would
boost the performance. If one of B or C fails, Postgres-XC fails (for this
release). But you can use coordinators on B and C simultaneously.


> **
>
> Now, we suppose that : server A and B are located in DC1, and serveur C
> and D are located in DC2.
>

Postgres-XC is not tolerant to network failures (right now). You will need
to test your deployment for this scenario.


> ****
>
> B and C will do the jobs and talk to A server (for GxId, sequence,..).****
>
> If DC2 fail, B (and A) servers will do the job.****
>
> If DC1 fail, we can promote D server to the master GTM and C server will
> do the job.****
>
> ** **
>
> ** **
>
> Is it all right ?****
>
> ** **
>
> ** **
>
> ** **
>
> Kriss_fr****
>
> ** **
>
> *De :* Ashutosh Bapat [mailto:ash...@en...]
> *Envoyé :* mercredi 30 janvier 2013 12:45
> *À :* Christophe Le Roux
> *Cc :* pos...@li...
> *Objet :* Re: [Postgres-xc-general] Table distribution/replication and
> other things****
>
> ** **
>
> Hi Christophe,
> Thanks for showing interest in Postgres-XC. Please find the answers below,
> inlined
>
> ****
>
> On Wed, Jan 30, 2013 at 4:31 PM, Christophe Le Roux <
> chr...@fr...> wrote:****
>
> Hi the team,****
>
>  ****
>
> First of all thank you for your work on postgresql XC. It’s a very cool
> features product, but I need more informations.****
>
>  ****
>
> My first question is about table distribution/replication :****
>
>                 Can we distribute and replicate a table ? (A table
> distributed on 3 datanodes (for performance) and replicated on 3 others
> datanode(for availability without down time) – I’m not talking about hot
> standby or streaming replication included in standard postgresql)****
>
>                 Is it in the roadmap to add this capability ?****
>
>  ****
>
>
> No, we can't have mixed distribution. You can use standbys for datanodes
> and coordinators using the streaming replication and hot standby
> capabilities of PostgreSQL. We do not have mixed distribution on our
> roadmap, right now.
>  ****
>
>  My second question is about GTM :****
>
>                 During how many time (30 seconds,5 min, 15 min, 1h ...)
> the GTM serveur can be down without impact the service (and without promote
> a GTM stanby to master) ?****
>
>               ****
>
>
> GTM provides the global transaction ids to datanodes and coordinators, so
> downtime allowed depends upon the transaction load, or rate of incoming
> transactions to the server. But, we don't have precise numbers here.
>  ****
>
>  My third question is about global architecture :****
>
>                 we have 2 datacenters with an extra low latency link (like
> LAN).****
>
> I want to put in the first DC one node with GTM and another with GTM
> proxy, coordinator and datanode and in the second DC one node with GTM
> standby and another node with GTM proxy,coordinator and datanode.****
>
> All tables of all databases will be replicated (DISTRIBUTE BY REPLICATION).
> ****
>
> Web server are in first and second DC.****
>
>  ****
>
> The goal is :****
>
> service is delivred by first and second DC at the same time****
>
> if one DC fail the service continue the other****
>
>  ****
>
>
> If I understand your deployment correctly, you are actually replicating
> the Postgres-XC setup at two DC's using standby servers. That may not work.
> We haven't tested this configuration.
>  ****
>
>                  What do you think about this ?****
>
>                 Can it be possible ?****
>
>  ****
>
>  ****
>
> Thank you****
>
>  ****
>
> Kriss_fr                                                   ****
>
>
>
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>
>
>
> --
> Best Wishes,
> Ashutosh Bapat
> EntepriseDB Corporation
> The Enterprise Postgres Company****
>



-- 
Best Wishes,
Ashutosh Bapat
EntepriseDB Corporation
The Enterprise Postgres Company