Re: Concurrent Users - Mailing list pgsql-admin

From Dustin Wenz
Subject Re: Concurrent Users
Date
Msg-id F5145E42-3BB3-49FC-A918-50E0BFF6172C@xtechllc.com
Whole thread Raw
In response to Concurrent Users  (shyam megha <shyamnguitar@gmail.com>)
List pgsql-admin
We have a number of medium-sized databases between 30 to 40TB that seem to perform well with some workloads. Our
applicationsare mostly insert-intensive, and we can do several thousand inserts per second with databases in that
range.Small inserts seem to be limited in performance by index updates, which need to be as efficient as possible.
Indexingsequential values like serial numbers and dates work well, but indexing random numbers like UUIDs does not work
well. 

It might be worth noting the number of file descriptors available to the user running your database. Postgres can burn
throughthem quickly with the default segsize. While I've not seen Postgres die from this, it doesn't help performance
ifit's rapidly opening and closing many thousands of data files. On ZFS, I've also seen performance improvements by
increasingthe blocksize higher than the default. 

I would not recommend putting all of your data in a small number of tables if you need maintenance tasks to run as fast
aspossible (vacuum full, dumps, restores, etc). Postgres is not great at parallelizing maintenance on individual
tables.It is, however, pretty good at distributing load between multiple concurrent users performing similar types of
queries.If you're only expecting 100 or so users, I don't think you'll have any problems. You will need to tune
parametersin postgresql.conf to match your hardware and workload, as described in many places online. 

The best advice I can give is to benchmark your schema and usage patterns. Create a database, and put as much data in
itas you ever could hope to need, and then even more. Performance will not change linearly; eventually you'll hit some
sortof wall. You'll want to know where that is sooner rather than later. 

    - .Dustin

On Aug 27, 2013, at 1:05 AM, shyam megha <shyamnguitar@gmail.com> wrote:

> Dear Psql Team,
>
> Hi there! I have two queries of Postgresql 9.x
>
> 1. What is the number of concurrent users who can access the PostgreSQL 9.x server at a time? Is it necessary for me
togo for Postgres Advanced Server plus or any other advanced edition  
>
> In our company we are looking for concurrent access of geospatial data by 100 users at a time.
>
> 2. Also is there maximum storage value that Postgres supports? We are planning to work with Terabytes of data.
>
>
>
> Regards,
> Sam



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