Most important MySQL Performance Tuning Variables and Status Variables.

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MySQL Performance Tuning
DOAG 2013 Datenbank
14. Mai 2013, Düsseldorf
Oli Sennhauser
Senior MySQL Berater, FromDual GmbH
oli.sennhauser@fromdual.com

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Über FromDual GmbH
● FromDual bietet neutral und unabhängig:
● Beratung für MySQL
● Support für MySQL und Galera Cluster
● Remote-DBA Dienstleistungen für MySQL
● MySQL Schulungen
● Oracle Silver Partner (OPN)
www.fromdual.com

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Inhalt
HA Solutions
➢
Read scale-out
➢
Replication set-up for HA
➢
Active/passive fail-over
➢
MySQL Cluster
➢
Replication Cluster
➢
Storage-Engine-Replication
MySQL Performance Tuning mit System-Variablen
➢
Performance Tuning Hebel
➢
MySQL System Variablen
➢
MySQL Status Variablen
➢
MySQL Architektur
➢
Speicherbelegung
➢
Session Variablen
➢
Globale Variablen
➢
MyISAM Variablen
➢
InnoDB Variablen
➢
Monitoring
➢
Informationen

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Performance Tuning Hebel

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MySQL System Variablen
● Datenbank-Konfiguration
my.cnf
mysqld ­­help –verbose
/etc/my.cnf /etc/mysql/my.cnf
/usr/local/mysql/etc/my.cnf
$basedir/my.cnf ~/.my.cnf
SHOW GLOBAL VARIABLES;

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MySQL Status Variablen
● Was wir damit anrichten sieht man mit:
SHOW /*!50001 GLOBAL */ STATUS;
SHOW ENGINE INNODB STATUSG

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MySQL Architektur
mysqld
Application / Client
Thread
Cache
Connection
Manager
User Au-
thentication
Command
Dispatcher
Logging
Query Cache
Module
Query
Cache
Parser
Optimizer
Access Control
Table Manager
Table Open
Cache (.frm, fh)
Table Definition
Cache (tbl def.)
Handler Interface
MyISAM Memory NDB PBXTInnoDB ...Aria XtraDB Tokutek

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Speicherbelegung
Storage Engines
MySQL Server (mysqld)
Client 2 Client N
Local Memory Areas
Client 1
read_buffer
sort_buffer
tmp_table
read_bufferread_buffer
sort_buffer
table_open_cache
table_definition_cache
query_cache_size
etc...
Global Memory Area
key_buffer_size
innodb_buffer_pool_size
innodb_log_buffer_size
etc...

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Thread Cache
● Konifguration:
thread_cache_size
● Status:
threads_created
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| Variable_name | Value |
+­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+
| Threads_cached | 8 |
| Threads_connected | 242 |
| Threads_created | 15355 |
| Threads_running | 16 |
+­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+

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Query Cache
● Konfiguration: query_cache_size
● Status:
Com_select,
Qcache_hits
● Hit ratio:
Qache_hits/(Com_select + Qcache_hits)
+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+
| Variable_name | Value |
+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+
| Com_select | 25712 |
| Qcache_free_memory | 19553200 |
| Qcache_hits | 65137 |
| Qcache_inserts | 172167 |
+­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­­­­+

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Per Session Parameter
● Im „Executor“
● Alloziert/Dealloziert „on Demand“
● Per Session oder global einstellbar
● Meisst Effekt gering oder gar kontraproduktiv!
● Join Buffer
● join_buffer_size
● Read Buffer und Read Random Buffer
● read_buffer_size, read_rnd_buffer_size

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Sort Buffer, temporäre Tabellen
●
Temporäre Tabellen
(MEMORY oder MyISAM)
● Konfiguration: tmp_table_size,
(max_heap_table_size)
● Status: created_tmp_tables,
created_tmp_disk_tables
●
Sort Buffer
● Konfiguration:
sort_buffer_size
● Status: sort_merge_passes

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Table Definition Cache
● Ab v5.1
● Enthält Info vom .frm File
● Konfiguration: table_definition_cache
● Status: open_table_definitions,
opened_table_defintions
+­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+
| Variable_name | Value |
+­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+
| Open_table_definitions | 100 |
| Opened_table_definitions | 100 |
+­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+

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Table (Open) Cache
● Ab v5.1
● File-Descriptioren (1 pro Connection pro Table)
● Früher table_cache
● Konfiguration: table_open_cache
● Status: open_tables, opened_tables
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| Variable_name | Value |
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| Open_tables | 64 |
| Opened_tables | 11812 |
+­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+

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MyISAM
● Bis MySQL 5.1 default Storage Engine
● Konfiguration: key_buffer_size
● Status: Key_blocks_used,
Key_blocks_unused, Key_reads,
Key_read_requests

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InnoDB Buffer Pool
● InnoDB seit 5.5 default Storage Engine
● InnoDB Buffer Pool
● Konfiguration:
innodb_buffer_pool_size,
innodb_buffer_pool_instances,
innodb_io_capacity
mysqld
system table space: ibdata1
table table space table table spacetable table space
ib_logfile1ib_logfile2ib_logfilen
undo
double write area
tables/indexes
dd
OS file cache
sync
async
buffer pool
secondary index buffer
trxlogbuffer
data pages
index pages
adaptive hash idx
undo records
lock info table

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InnoDB Buffer Pool
● Status:
innodb_buffer_pool_pages_%,
Innodb_buffer_bytes_%,
Innodb_data_%

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InnoDB Log File
● REDO Log, Transaction
Log
● Konfiguration:
innodb_log_file_size,
innodb_flush_log_at_trx
_commit
● Status: innodb%log%
mysqld
system table space: ibdata1
table table space table table spacetable table space
ib_logfile1ib_logfile2ib_logfilen
undo
double write area
tables/indexes
dd
OS file cache
sync
async
buffer pool
secondary index buffer
trxlogbuffer
data pages
index pages
adaptive hash idx
undo records
lock info table

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Binary Log
Application ApplicationApplication
mysqld
bin-log.n
binlog_cache_size
binlog_stmt_cache_size
sync_binlog
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+
| Variable_name | Value |
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+
| Binlog_cache_disk_use | 3456 |
| Binlog_cache_use | 12786 |
| Binlog_stmt_cache_disk_use | 0 |
| Binlog_stmt_cache_use | 0 |
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­+­­­­­­­+

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Monitoring
● Von Hand:
● SHOW GLOBAL STATUS;
● SHOW ENGINE INNODB STATUSG
● Performance Schema (P_S, >= v5.5)
● Irgend ein graphisches Monitoring Tool...

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PERFORMANCE_SCHEMA
● In Diskussion seit mindestens 2006
● Eingeführt in MySQL 5.5 (2010)
→ Einblick in die Datenbank
● In v5.5 disabled, in v5.6 enabled per default
performance_schema = 1
● Overhead 5% - 200%! → also Vorsicht!

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Beispiel: Table I/O waits
SELECT OBJECT_SCHEMA, OBJECT_NAME
, ROUND(SUM_TIMER_WAIT/1000000000, 3) AS SUM_TIMER_WAIT
, ROUND(SUM_TIMER_READ/1000000000, 3) AS SUM_TIMER_READ
, ROUND(SUM_TIMER_WRITE/1000000000, 3) AS SUM_TIMER_WRITE
FROM table_io_waits_summary_by_table
ORDER BY SUM_TIMER_WAIT DESC
LIMIT 10
;
+­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+
| OBJECT_SCHEMA | OBJECT_NAME | SUM_TIMER_WAIT | SUM_TIMER_READ | SUM_TIMER_WRITE |
+­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+
| zabbix | items | 1182496.258 | 616630.696 | 565865.562 |
| zabbix | history_uint | 889884.116 | 370528.991 | 519355.125 |
| zabbix | history_str | 460411.155 | 246159.458 | 214251.697 |
| zabbix | history | 389815.659 | 86285.980 | 303529.679 |
| zabbix | trends_uint | 133955.560 | 107365.626 | 26589.934 |
| zabbix | functions | 128657.654 | 128657.654 | 0.000 |
| zabbix | trends | 43683.159 | 36314.732 | 7368.428 |
| mpm | mpm_agent | 27837.056 | 27837.056 | 0.000 |
| zabbix | hosts | 23820.284 | 14044.672 | 9775.612 |
| zabbix | triggers | 21052.459 | 20970.604 | 81.855 |
+­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­+­­­­­­­­­­­­­­­­­+

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Informationen
● MySQL System Variablen:
http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html
● MySQL Status Variablen:
http://dev.mysql.com/doc/refman/5.5/en/server-status-variables.html
● MySQL DB Health Check:
http://www.fromdual.com/mysql-database-health-check
● MySQL Performance Monitor:
http://www.fromdual.com/mysql-performance-monitor

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Q & A
Fragen ?
Diskussion?
Wir haben Zeit für ein Performance Audit...!
● FromDual bietet neutral und unabhängig:
● Beratung
● Remote-DBA
● Support für MySQL und Galera Cluster
● Schulung
www.fromdual.com/presentations