Re: [Postgres-xc-general] Infrastructure Suggestions

For datanodes, you can configure it much like PostgreSQL. But
coordinators are a bit tricky.

If you have distributed your tables such that most of your queries are
being run on datanode, you can do with medium sized work mem. You
don't need much buffer space, except for catalog queries. Now, how do
we detect, how much of the query is being run on the datanode? In the
explain outputs of plans steps with labels "Data node scan" are
executed on datanodes, whereas any other steps are run at coordinator.
If you see a lot of steps being executed on the coordinator, you need
more memory and CPU resources at the coordinator.

On Wed, Jan 16, 2013 at 4:49 AM, Michael Paquier
<mic...@gm...> wrote:
>
>
> On Wed, Jan 16, 2013 at 12:41 AM, Arni Sumarlidason
> <Arn...@md...> wrote:
>>
>> Good Morning Everyone,
>>
>>
>>
>> We are setting up a 25 node postgres-xc cluster, does anyone have suggests
>> on how much disk space a coordinator uses with its local database?
>
> Not that much, Coordinator contains only catalog information. I let at your
> appreciation the amount of space you think you need, but not gigs for sure.
>
>> Also hints regarding the memory section in postgresql.conf would be
>> awesome!
>
> I would do the settings of shared_buffers, work_mem, maintenance_work_mem
> and effective cache size on Datanodes as on normal PostgreSQL servers.
> For Coordinators, you don't need that much memory except if you have sort
> operations happening there, in this case adapt work_mem. You can also set up
> shared_buffers to put all the catalog information on-cache, but I do not
> think it is that much a win.
>
> Thanks,
> --
> Michael Paquier
> http://michael.otacoo.com
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-- 
Best Wishes,
Ashutosh Bapat
EntepriseDB Corporation
The Enterprise Postgres Company