MySQL高性能以及高安全測試

時間 2019-11-18

原文原文鏈接

1. 參數描述

Command-Line Formatmysql	--sync-binlog=#sql
Option-File Format緩存	sync_binlog安全
System Variable Nameapp	sync_binlogless
Variable Scopeasync	Global函數
Dynamic Variable性能	Yes
	Permitted Values
	Platform Bit Size	32
	Type	numeric
	Default	0
	Range	0 .. 4294967295
	Permitted Values
	Platform Bit Size	64
	Type	numeric
	Default	0
	Range	0 .. 18446744073709547520

If the value of this variable is greater than 0, the MySQL server synchronizes its binary log to disk (using fdatasync()) after sync_binlog commit groups are written to the binary log. The default value of sync_binlog is 0, which does no synchronizing to disk—in this case, the server relies on the operating system to flush the binary log's contents from time to time as for any other file. A value of 1 is the safest choice because in the event of a crash you lose at most one commit group from the binary log. However, it is also the slowest choice (unless the disk has a battery-backed cache, which makes synchronization very fast).

sync_binlog參數說明：

當sync_binlog是控制事務寫入二進制日誌的方式。若是設置大於0，則達到sync_binlog設置的值一組事務同步寫入到二進制日誌；若是設置爲0，則每當事務發生，在內存中的事務信息，不是同步刷到磁盤，而是依賴於操做系統時常刷新到磁盤；當設置爲1，則是更安全的選項，當宕機後，最多失去1個事務的信息，可是性能確實最慢的。

innodb_flush_log_at_trx_commit

Command-Line Format	--innodb_flush_log_at_trx_commit[=#]
Option-File Format	innodb_flush_log_at_trx_commit
System Variable Name	innodb_flush_log_at_trx_commit
Variable Scope	Global
Dynamic Variable	Yes
	Permitted Values
	Type	enumeration
	Default	1
	Valid Values	0
		1
		2

Controls the balance between strict ACID compliance for commit operations, and higher performance that is possible when commit-related I/O operations are rearranged and done in batches. You can achieve better performance by changing the default value, but then you can lose up to one second worth of transactions in a crash.

The default value of 1 is required for full ACID compliance. With this value, the log buffer is written out to the log file at each transaction commit and the flush to disk operation is performed on the log file.
With a value of 0, any mysqld process crash can erase up to a second of transactions. The log buffer is written out to the log file once per second and the flush to disk operation is performed on the log file. No writes from the log buffer to the log file are performed at transaction commit. Once-per-second flushing is not 100% guaranteed to happen every second, due to process scheduling issues.
With a value of 2, any mysqld process crash can erase up to a second of transactions. The log buffer is written out to the log file at each commit. The flush to disk operation is performed on the log file once per second. Once-per-second flushing is not 100% guaranteed to happen every second, due to process scheduling issues.
As of MySQL 5.6.6, InnoDB log flushing frequency is controlled by innodb_flush_log_at_timeout, which allows you to set log flushing frequency to N seconds (where Nis 1 ... 2700, with a default value of 1). However, any mysqld process crash can erase up to N seconds of transactions.
DDL changes and other internal InnoDB activities flush the InnoDB log independent of the innodb_flush_log_at_trx_commit setting.
InnoDB's crash recovery works regardless of the innodb_flush_log_at_trx_commit setting. Transactions are either applied entirely or erased entirely.

For durability and consistency in a replication setup that uses InnoDB with transactions:

If binary logging is enabled, set sync_binlog=1.
Always set innodb_flush_log_at_trx_commit=1.

Caution

Many operating systems and some disk hardware fool the flush-to-disk operation. They may tell mysqld that the flush has taken place, even though it has not. Then the durability of transactions is not guaranteed even with the setting 1, and in the worst case a power outage can even corrupt InnoDBdata. Using a battery-backed disk cache in the SCSI disk controller or in the disk itself speeds up file flushes, and makes the operation safer. You can also try using the Unix command hdparm to disable the caching of disk writes in hardware caches, or use some other command specific to the

innodb_flush_log_at_trx_commit參數說明：

innodb_flush_log_at_trx_commit=1，徹底尊周ACID事務的原則，每提交一次，log buffer中的日誌刷新到log file的文件緩存，而後在刷新到磁盤。這種的性能最差。當innodb_flush_log_at_trx_commit=0的時候，當mysqld宕掉的時候，會丟失一秒的事務，每1秒log buffer中的日誌會先寫到log file的文件緩存，而後經過操做系統調度，時常刷新到磁盤。當爲innodb_flush_log_at_trx_commit=2，會丟失一秒的事務，每次提交log buffer的日誌會寫到日誌文件緩存，日誌文件緩存中的日誌刷新到磁盤則是每秒鐘發生。