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Mysql tuning!!!!

Discussion in 'Database Discussions' started by supportech, May 3, 2011.

  1. supportech

    supportech Member

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    Hi

    The server keeps crashing because of large number of httpd requests from user nobody. Can anyone please look into this and advice. Here are the mysqltuner recommendations and my.cnf details

    =====================
    /usr/local/cpanel/3rdparty/mysqltuner/mysqltuner.pl

    >> MySQLTuner 1.1.2 - Major Hayden <major@mhtx.net>
    >> Bug reports, feature requests, and downloads at http://mysqltuner.com/
    >> Run with '--help' for additional options and output filtering

    -------- General Statistics --------------------------------------------------
    [--] Skipped version check for MySQLTuner script
    [OK] Currently running supported MySQL version 5.0.92-community
    [OK] Operating on 64-bit architecture

    -------- Storage Engine Statistics -------------------------------------------
    [--] Status: +Archive -BDB -Federated -InnoDB -ISAM -NDBCluster
    [--] Data in MyISAM tables: 3G (Tables: 496)
    [--] Data in MEMORY tables: 0B (Tables: 2)
    [!!] Total fragmented tables: 55

    -------- Performance Metrics -------------------------------------------------
    [--] Up for: 4m 34s (51K q [187.117 qps], 1K conn, TX: 803M, RX: 7M)
    [--] Reads / Writes: 93% / 7%
    [--] Total buffers: 1.1G global + 10.6M per thread (500 max threads)
    [OK] Maximum possible memory usage: 6.3G (54% of installed RAM)
    [OK] Slow queries: 0% (5/51K)
    [OK] Highest usage of available connections: 9% (46/500)
    [OK] Key buffer size / total MyISAM indexes: 8.0M/191.2M
    [OK] Key buffer hit rate: 99.9% (8M cached / 6K reads)
    [OK] Query cache efficiency: 73.3% (33K cached / 46K selects)
    [OK] Query cache prunes per day: 0
    [OK] Sorts requiring temporary tables: 0% (39 temp sorts / 4K sorts)
    [!!] Temporary tables created on disk: 48% (3K on disk / 7K total)
    [OK] Thread cache hit rate: 90% (138 created / 1K connections)
    [OK] Table cache hit rate: 98% (301 open / 307 opened)
    [OK] Open file limit used: 15% (385/2K)
    [OK] Table locks acquired immediately: 99% (19K immediate / 19K locks)

    -------- Recommendations -----------------------------------------------------
    General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    MySQL started within last 24 hours - recommendations may be inaccurate
    Enable the slow query log to troubleshoot bad queries
    Temporary table size is already large - reduce result set size
    Reduce your SELECT DISTINCT queries without LIMIT clauses
    ========================

    # cat /etc/my.cnf
    [mysqld]
    datadir=/var/lib/mysql
    skip-locking
    safe-show-database
    skip-innodb
    max_user_connections=100
    max_connections=500
    interactive_timeout=100
    wait_timeout=100
    connect_timeout=20
    max_connect_errors=20
    max_allowed_packet=32M
    query_cache_limit=1M
    query_cache_size=128M
    query_cache_type=1

    read_buffer_size=8M
    tmp_table_size=1024M
    max_heap_table_size=1024M
    thread_cache_size=6
    table_cache=1024

    [mysql.server]
    user=mysql

    [safe_mysqld]
    err-log=/var/log/mysqld.log
    pid-file=/var/lib/mysql/mysql.pid
    open_files_limit=8192

    [mysqldump]
    quick
    max_allowed_packet=32M

    [mysql]
    no-auto-rehash
    =======================
     
  2. cPanelTristan

    cPanelTristan Quality Assurance Analyst
    Staff Member

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    At this point in time, what makes you believe MySQL has any correlation to the machine crashing? MySQL always shows high CPU usage on most machines, which does not mean it is the cause for any crash. Basically, have you had a qualified system administrator review the machine during the crash to determine it is MySQL as the cause?

    I ask this as a large number of httpd requests running as nobody instead indicates that Apache has high connections and activity on your machine. MySQL might not be related to the high load at all. Possibly, the machine is getting a DoS attack, or it might be hitting memory or CPU limits for Apache processing. This would indicate a need to optimize Apache or setup filtering for a denial of service. I have a thread where I discussed a possible DoS attack and how to troubleshoot one of these happening:

    http://forums.cpanel.net/f5/how-restart-apache-trough-cpanel-command-line-187252.html#post766101

    Since you've already had a prior thread about MySQL optimization and you aren't receiving any further suggestions by mysqltuner.pl for changing values in your configuration itself, it seems you may want to look elsewhere (such as Apache) for the heart of the issue.
     
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