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  1. #1
    Join Date
    Apr 2006

    Unanswered: Performance Issues


    We are currently developing a web application and have the webserver and PostgreSQL with our dev db running on a machine with these specs:

    Win 2003 standard
    AMD Athlon XP 3000 / 2.1 GHZ
    2 Gig ram
    120 gig SATA HD
    PostgreSQL 8.1.0
    Default pgsql configuration + shared buffers = 30,000

    The performance of postgresql and our web application is good on that machine, but we decided to build a dedicated database server for our production database that scales better and that we can also use for internal applications (CRM and so on).

    To make a long story short, we built a machine with these specs:

    Windows 2003 Standard
    AMD Opteron 165 Dual Core / running at 2 GHZ
    2 gig ram
    2 x 150 Gig SATA II HDs in RAID 1 mode (mirror)
    PostgreSQL 8.1.3
    Default pgsql configuration + shared buffers = 30,000

    Perfomance tests in windows show that the new box outperforms our dev machine quite a bit in CPU, HD and memory performance.

    I did some EXPLAIN ANALYZE tests on queries and the results were very good, 3 to 4 times faster than our dev db.

    However one thing is really throwing me off.
    When I open a table with 320,000 rows in the pgadmin tool (v 1.4.0) it takes about 6 seconds on the dev server to display the result (all rows). During these 6 seconds the CPU usage jumps to 90%-100%.

    When I open the same table on the new, faster, better production box, it takes 28 seconds!?! During these 28 seconds the CPU usage jumps to 30% for 1 second, and goes back to 0% for the remaining time while it is running the query.

    What is going wrong here? It is my understanding that postgresql supports multi-core / cpu environments out of the box, but to me it appears that it isn't utilizing any of the 2 cpu's available. I doubt that my server is that fast that it can perform this operation in idle mode.

    I played around with the shared buffers and tried out versions 8.1.3, 8.1.2, 8.1.0 with the same result.

    Has anyonce experienced this kind of behaviour before?
    How representative is the query performance in pgadmin?

    I appreciate your ideas, comments and help.


  2. #2
    Join Date
    Feb 2005
    Colorado Springs
    There has been some discussion of performance issues on the PostgreSQL General mailing list. Perhaps you might look at those threads and maybe get some advice from the development team on that website.

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