故障描述：主从架构，主宕机后，切换到了从，结果从上数据丢失了很多（在没宕机前未校验数据一致性），当时同步没有延时，用户登录时，无法在数据库中验证，结果
故障描述：主从架构，主宕机后，切换到了从，结果从上数据丢失了很多（在没宕机前未校验数据一致性），当时同步没有延时，用户登录时，无法在数据库中验证，结果大批用户无法登陆，导致投诉。
之前我写过一个PPT，是如何校验主从数据是否一致性。
主从同步正常，香港虚拟主机，并不代表主从数据一致性，香港虚拟主机，为什么？我举例说明一下：
主库上有a用户，密码123456，香港虚拟主机，从库上没有该用户。如果a用户一直不更新密码，从库上你用show slave status\G，发现是没有任何报错信息的，因为没有触发这条记录。不信，你可以试试。
所以才会有下面这个工具的存在：（注意！这个工具会锁表，表越大，锁住的时间也会越长）
注：主从架构，必须要保证数据的一致性，避免造成今天我这边的特大故障！
本文出自 “贺春旸的技术专栏” 博客，请务必保留此出处
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