MySQL 升级的最佳实践

川长思鸟来 2022-08-18 01:59 206阅读 0赞

# MySQL 升级的最佳实践 #

转自：http://www.oschina.net/translate/mysql-upgrade-best-practices

MySQL升级是非常必要的. 我们在[Percona Support][]上列出了关于MySQL升级最佳实践的各种问题.这篇文章推荐了一些不同情况下升级MySQL的方法.

为什么MySQL升级是必须的? 原因有很多,比如：为了使用新增的特性,基于性能方面的考量, 修复的bug. 但是在没有充分的测试以前就应用到你的应用中是非常危险的, 因为升级可以能会让你的应用不能正常运作- 也可能引起性能的问题. 此外, 我建议你关注MySQL的发布信息和[Percona Server][] - 看看最近的版本有什么变化. 也许在在最新的版本中已修复了某个你正在烦恼的问题.

通过SQL Dump升级主版本:

把Percona Server从5.1升级到5.5版本或者是从5.5升级到5.6版本的升级模式同样适用于Oracle MySQL.

首先, 主版本升级并不是说可以不做任何准备,或者没有任何风险. 在升级之前你需要阅读相关的“升级”文档,比如:MySQL5.1到MySQL5.5的[升级文档][Link 1],MySQL5.5到MySQL5.6的[升级文档][Link 2].在这些文档里面你需要特别注意“Incompatible Change”部分,并检查你是否会受到这些变化的影响.它们可能是配置参数名字变更, 去掉旧的参数,引入新的参数等- 你需要根据这些变化在my.cnf文件做相应的变更.Percona Server 5.5需要特别注意的文档在[这里][Link 3], Percona Server 5.6需要特别注意的文档在[这里][Link 4].

现在，你有几种可行的方式升级，其中一种较灵活，另一种则依赖你当前系统的拓扑结构和数据库数据大小 - 这种方法比前一种更安全。我们看个例子从 [Percona Server][Percona Server 1] 5.5 升级到 Percona Server 5.6，来具体看一下彼此的升级过程。

通常情况下，有两中升级方式：

*  直接升级:安装好新版本数据库后，利用已经存在的数据文件夹，同时运行mysql\_upgrade脚本来升级。
 *  SQL 导出： 从一个较老版本的mysql把数据导出，然后恢复到新版本的数据库中。(利用mysqldump工具)。

相比之下，第二种方式更安全些，但是这也会使得升级的过程要慢一些。

理论上讲，最安全的方式是：

*  导出所有用户的权限
 *  导出所有数据并恢复到新版本数据库中
 *  恢复用户权限到新数据库中

下面是基本的操作步骤(在开始之前最好停止有关数据库操作的应用).

1) 获取用户和权限信息. 该操作会备份所有用户的权限.

[?][Link 5]

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      2 
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2) dump 5.5数据库实例的所有信息(除去mysql, information\_schema 和performance\_schema数据库).

[?][Link 5]

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 </tbody> 
</table>

3) 停止数据库

[?][Link 5]

<table style="width:750px; margin:0px!important; padding:0px!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
 <tbody style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
  <tr style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
   <td style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(175,175,175)!important; background:none!important"> 
    <div style="margin:0px!important; padding:0px 0.5em 0px 1em!important; border-width:0px 3px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important; background:none rgb(248,248,248)!important">
      1 
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      2 
    </div> 
    <div style="margin:0px!important; padding:0px 0.5em 0px 1em!important; border-width:0px 3px 0px 0px!important; border-right-style:solid!important; border-right-color:rgb(108,226,108)!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; text-align:right!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important; background:none rgb(248,248,248)!important">
      3 
    </div> </td> 
   <td style="width:717px; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
    <div style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important; background:none rgb(248,248,248)!important"> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">$&nbsp;service&nbsp;mysql&nbsp;stop</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">or</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important; background:none rgb(248,248,248)!important"> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">$&nbsp;</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">/etc/init</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">.d</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">/mysql</code>&nbsp; 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">stop</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

4) 移动旧数据库(5.5版本)的数据目录(假设是/var/lib/mysql,此处应该改为你自己的数据目录)

[?][Link 5]

5) 安装5.6版本(按照正常安装流程). 如果你不是用的yum/apt-get方式安装的,你需要执行 [mysql\_install\_db][mysql_install_db] 和mysql\_upgrade两个命令.

6) 将在1)操作中导出的用户信息导入到新数据库中.

[?][Link 5]

7) 将2)导出的数据导入到新数据库.

[?][Link 5]

<table style="width:750px; margin:0px!important; padding:0px!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
 <tbody style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
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   <td style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(175,175,175)!important; background:none!important"> 
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      1 
    </div> 
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      2 
    </div> </td> 
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    <div style="margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; background:none!important"> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important; background:none rgb(248,248,248)!important"> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">$&nbsp;mysql&nbsp;-e&nbsp;</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:blue!important; background:none!important">"SET&nbsp;GLOBAL&nbsp;max_allowed_packet=1024*1024*1024"</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">;</code> 
     </div> 
     <div style="margin:0px!important; padding:0px 1em!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">$&nbsp;mysql&nbsp;-uroot&nbsp;-p&nbsp;--max-allowed-packet=1G&nbsp;&lt;&nbsp;</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">/root/full-data-dump</code> 
      <code style="white-space:nowrap; margin:0px!important; padding:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">.sql;</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

此时, 所有的表都在MySQL 5.6中重建及重新加载完成,所以所有的二进制文件对MySQL 5.6可用. 同时也你完成了最干净/最稳定的升级过程,你可以恢复你的应用- 这个升级过程和valina MySQL与Percona Server的升级过程是一样的.甚至你可以把Oracle MySQL升级到Percona Server. 比如: 把Oracle MySQL 5.5升级到Percona Server 5.6. 再次强调: MySQL的升级过程和Percona Server的升级过程是一样的,只需要将Percona Server 替换成Oracle MySQL即可.

"SQL dump" 也可以称为逻辑备份.用升级后的MySQL二进制文件来重建所有的表基本没有兼容问题,从这一方面来说"SQL dump"更安全. 但是对于TB, GB级的大数据来说,这种方法非常的耗时. 另一方面, 备份/重新加载如此大的数据集,比如重建InnoDB表,你需要恢复很多的空闲磁盘,这样会引起的磁盘碎片整理优化.对于常更新或者删除的数据来说, 这么做是有益的.

用In-Place升级小版本:

这种升级方式是在一个主版本内做小版本升级, 比如把MySQL 5.5.35升级到MySQL 5.5.38或者是把Percona Server 5.6.14升级到最新的Percona Server 5.6.20

这被称为一个就地升级,你只安装一个新的二进制包,然后运行[mysql\_upgrade][mysql_upgrade]脚本,如果必要的话,检查和更新系统表。仍然,就地升级我们强烈推荐检查新功能的发布说明,bug修复等。Percona Server 5.5 和 Percona Server 5.6 发行说明可以分别在[这儿][Link 6][和那儿][mysql_upgrade]找到。

当我们需要升级Percona服务器时，针对它的Percona-specific的一些特性,对于Percona服务器我们有额外的文档描述一些细节，可以在这儿和那儿找到。这也包括完成就地升级过程的和yum/apt的包管理器。

同时,在安全方面你可以升级那些使用较早描述的逻辑转储程序,mysqldump或mydumper程序——前者并行备份和恢复和逻辑备份,升级是最安全的方法。

直接升级到最新版本:

跳过5.1版本直接把MySQL从5.0版本升级到5.5版本,或者跳过5.5版本直接从MySQL 5.1升级到5.6.甚至,可以直接从MySQL 5.0升级到MySQL 5.6虽然现在只有少数人还在使用MySQL 5.0版本. 这种同样使用于Percona Server.

在这里我们假设跳过5.5版本,把Oracle MySQL或者Percona Server直接从5.1版本升级到5.6版本.

在开始之前，你要意识到这是一个很慎重的操作，将一步跨过一个重要的MySQL版本。也就是说，这是有风险的。用二进制文件升级是不建议的，而且这样直接跨越一个重要版本也是不安全的，所以你绝不能这样5.0->5.5,5.1->5.6,或者5.0->5.6做。有一个问题是，MySQL版本不是所有改变都前向兼容的。新版本中介绍的一些改变可能不仅会影响数据如何处理，还会影响服务器行为包括SQL语句和MySQL服务器和内部存储引擎（此处不知标准否）。另一个问题是MySQL5.0与5.6版本之间的变化，一些默认的设置变量被改变了，这可能会导致结果完全不一样或者行为完全不同。例如：MySQL5.5的默认存储引擎是InnoDB，MySQL5.6的存储引擎[InnoDB][]将可以为每个数据库表创建单独表空间（[separate tablespace][]），还有GTID复制（[GTID][] replication）也被引入。有太多细节这里就不一一列举了，所有这些改变都被描述在MySQL的“升级文档”中，详情可以查看升级文档。

这里重点提一下，极不推荐跳过一个重要版本来升级。从MySQL5.1升级到5.6不应该一步完成，我建议先从5.1升级到5.5，再从5.5升级到5.6，每步都要运行MySQL自动升级（mysql\_upgrade）。这将比较有效处理手册上所说的升级改变。

MySQL的升级预防措施：

MySQL的升级预防措施是升级的一个基本部分。在你升级之前，确保你在新的MySQL版本中彻底测试了所有的应用功能。这对重要版本之间的升级尤为重要，对重要版本之间的跨越升级也很重要（例如，从MySQL5.1升级到MySQL5.6）。

确保你认真阅读了发行说明，并且你清楚所有改变。你可以从以下链接中获取Oracle MySQL 5.5和5.6的发行说明：

[http://dev.mysql.com/doc/relnotes/mysql/5.5/en/][http_dev.mysql.com_doc_relnotes_mysql_5.5_en]

[http://dev.mysql.com/doc/relnotes/mysql/5.6/en/][http_dev.mysql.com_doc_relnotes_mysql_5.6_en]

[Percona Server][Percona Server 1]有单独的发行说明，按上面说的顺序可以参看以下链接：

[http://www.percona.com/doc/percona-server/5.5/release-notes/release-notes\_index.html][Link 6]  
[http://www.percona.com/doc/percona-server/5.6/release-notes/release-notes\_index.html][mysql_upgrade]

如果你计划升级到 Oracle MySQL 5.6 或者 Percona Server 5.6，我建议你首先检查以下已经存在的关键bugs。以下是你需要注意的一些bugs：

[http://bugs.mysql.com/bug.php?id=66546][http_bugs.mysql.com_bug.php_id_66546]  
[http://bugs.mysql.com/bug.php?id=68953][http_bugs.mysql.com_bug.php_id_68953]  
[http://bugs.mysql.com/bug.php?id=69444  
][http_bugs.mysql.com_bug.php_id_69444][http://bugs.mysql.com/bug.php?id=70922][http_bugs.mysql.com_bug.php_id_70922]  
[http://bugs.mysql.com/bug.php?id=72794][http_bugs.mysql.com_bug.php_id_72794]  
[http://bugs.mysql.com/bug.php?id=73820][http_bugs.mysql.com_bug.php_id_73820]

升级的层次结构：

这也是每一次MySQL升级的关键。你需要根据一个升级层次结构来做你的每次升级。建议的次序结构是：首先升级 dev/QA servers，然后升级 staging server，最后升级到 production servers上。实际上，你可以缩小升级的步伐，一步一步升级到你想要的版本，每步都可以充分地测试原来的应用。

一旦你对在test servers, staging servers等上运行的升级感到满意后，你就可以在你的production servers上进行升级了。在副本环境下，我建议你先升级MySQL slaves（一个接一个的）最后升级MySQL master。实际上，你可以先升级一个slaves，让它在安全环境下运行几天，同时观察仔细观察它的运行情况。如果你的服务器中没有副本环境的设置，那么还是值得建立一个副本环境来测试新版的MySQL的。一旦你对升级结果感到满意，你可以升级其他的slaves，最后升级master。

Percona软件包帮助你MySQL升级：

在MySQL升级中，[Percona Toolkit ][Percona Toolkit]都能帮助你。Percona Toolkit 的一些工具将会起到很大的作用。

[pt-upgrade][] 是其中的一个工具。它使你能测试新版MySQL实例是否能够达到像老版本处理一些特定查询的时候一样的速度。新版本可能有一些本质上的改变，因为MySQL的查询优化器从5.1到5.6已经有了重大改变，还有数据统计可能刷新，因此查询计划会改变。你可以在[手册][Link 7]中看到更多优化器的改变。

[pt-query-digest][] 是另一个能给你极大帮助的工具。你可以多次运行你的slow query log，以比较确认在现在的版本和新版本之间的表现差别。

你也可以从MySQL的[Percona Cloud Tools][]中获得帮助，这是一个托管服务，可以为所有MySQL的使用提供查询性能分析。现在你可以免费注册这个服务，因为现在这项服务在进行公开测试。Percona Cloud Tools在许多同类产品中，能让你可视化的观察到每次MySQL升级后的查询表现。

再次重申，强烈建议你每次更新MySQL前备份数据。[Percona XtraBackup][]就是一款免费、开源的（就像所有Percona软件一样）。这是一个热备份工具，它允许你在线备份数据而不影响你对数据库的读写操作，而且它备份数据时产生很小的影响。

最后，你会觉得这个[帖子][Link 8]也是很有用的”Upgrading MySQL.“虽然已经是老帖子了，但是还是比较有意义的。再看一个有意义的文章[webinar][]，”Upgrading to MySQL 5.6: Best Practices.“。这两篇文都出自Percona CEO Peter Zaitsev。

结论：

一次MySQL升级看起来是个简单的任务，但实际上并没有那么简单。我试图在这篇文章中最大限度覆盖所有有关MySQL升级中你可能遇到的情况。再次强调，我建议你在应用更新的版本之前，先测试一下你的应用在新版本中的效果。否则，可能会使你的应用崩溃，或者得到的不是提高查询效率而是降低查询效率。最后，我建议你准备一个降级计划或措施，以防你升级之后出现不可预料的错误。在问题出现的时候，有一个规划好的降级程序将会极大的减少你的应用停工期。期待你在下面发表评论和提问。

[Percona Support]: http://www.percona.com/products/mysql-support
[Percona Server]: http://www.percona.com/software/percona-server
[Link 1]: http://dev.mysql.com/doc/refman/5.5/en/upgrading-from-previous-series.html
[Link 2]: http://dev.mysql.com/doc/refman/5.6/en/upgrading-from-previous-series.html
[Link 3]: http://www.percona.com/doc/percona-server/5.5/upgrading_guide_51_55.html#changes-in-server-configuration
[Link 4]: http://www.percona.com/doc/percona-server/5.6/changed_in_56.html
[Percona Server 1]: http://www.oschina.net/p/percona+server
[Link 5]: http://www.oschina.net/translate/mysql-upgrade-best-practices#
[mysql_install_db]: http://dev.mysql.com/doc/refman/5.5/en/mysql-install-db.html
[mysql_upgrade]: http://www.percona.com/doc/percona-server/5.6/release-notes/release-notes_index.html
[Link 6]: http://www.percona.com/doc/percona-server/5.5/release-notes/release-notes_index.html
[InnoDB]: http://www.oschina.net/p/innodb
[separate tablespace]: http://dev.mysql.com/doc/refman/5.5/en/innodb-multiple-tablespaces.html
[GTID]: http://dev.mysql.com/doc/refman/5.6/en/replication-gtids-concepts.html
[http_dev.mysql.com_doc_relnotes_mysql_5.5_en]: http://dev.mysql.com/doc/relnotes/mysql/5.5/en/
[http_dev.mysql.com_doc_relnotes_mysql_5.6_en]: http://dev.mysql.com/doc/relnotes/mysql/5.6/en/
[http_bugs.mysql.com_bug.php_id_66546]: http://bugs.mysql.com/bug.php?id=66546
[http_bugs.mysql.com_bug.php_id_68953]: http://bugs.mysql.com/bug.php?id=68953
[http_bugs.mysql.com_bug.php_id_69444]: http://bugs.mysql.com/bug.php?id=69444
[http_bugs.mysql.com_bug.php_id_70922]: http://bugs.mysql.com/bug.php?id=70922
[http_bugs.mysql.com_bug.php_id_72794]: http://bugs.mysql.com/bug.php?id=72794
[http_bugs.mysql.com_bug.php_id_73820]: http://bugs.mysql.com/bug.php?id=73820
[Percona Toolkit]: http://www.oschina.net/p/percona-toolkit
[pt-upgrade]: http://www.percona.com/doc/percona-toolkit/2.2/pt-upgrade.html
[Link 7]: http://dev.mysql.com/tech-resources/articles/whats-new-in-mysql-5.6.html#optimizer
[pt-query-digest]: http://www.percona.com/doc/percona-toolkit/2.2/pt-query-digest.html
[Percona Cloud Tools]: https://cloud.percona.com/
[Percona XtraBackup]: http://www.oschina.net/p/xtrabackup
[Link 8]: http://www.percona.com/blog/2010/01/05/upgrading-mysql/
[webinar]: http://www.percona.com/resources/mysql-webinars/upgrading-mysql-56-best-practices