Linux Ext3下删除MySQL数据库的数据恢复案例
[其他] 1、Linux Ext3数据删除后应尽快断掉文件系统IO,通常umount文件系统即可。 2、对故障卷做dd备份,确保数据恢复过
[数据恢复故障描述]
一台重要的MySQL数据库服务器,146GB*2,RAID1,约130GB DATA卷,存储了大约200~300个数据库。平时管理员对每个数据库dump出以后,直接压缩成.gz包,再将所有重要的.gz 包合起来压缩成一个总的.tar.gz包,这些文件每日产生一次,覆盖原来的备份。数据文件及备份文件全部存储于data卷上。
一次系统维护中,管理员不小心将data卷下的所有文件全部rm,删除后,马上停止系统,再未做其它操作,但删除时仍有大量终端在访问此服务器。
要求恢复MySQL数据库文件,即myd、frm、myi(可重建)文件,或每个数据库的.gz包,或所有重要数据库总的.tar.gz备份包。
[数据恢复分析]
Ext3下的数据删除,理论上,会清除inode中除节点类型、日期外的其他属性,诸如文件大小、数据存储地址等属性会全部清0,同时目录表中会以目录条目长度的方式屏蔽掉已删除文件,但会保留节点编号,最后会改变BITMAP中的空间占用标志。
即使是目录表中存在删除文件的节点编号,但因节点内容已经没有需要的东西,与数据区也是脱钩的。
从数据角度,大多数文件类型都会有特定的文件头标志,按头标志是有可能找到删除文件的起始位置的,但EXT3以块组为单位进行存储,同时数据与索引是混合存储于数据区的,所以数据连续存储的可能性非常之小,这样,按文件格式进行处理也是很困难的。
唯一的算法是结合上述几个特征,加上对日志的分析,加上对存储过程的模拟分析,尽可能地逼近真实存储结构。
[数据恢复过程]
1、对故障卷做完整备份。
2、对总.tar.gz进行恢复分析,但恢复出来的文件解压到50%左右会报错,后续文件列表也无法列出。经分析,最大的原因是删除时仍有数据写入破坏文件导致。
3、对分包的.gz文件进行恢复分析,大多数恢复成功。
4、对于未恢复成功的.gz数据库。直接恢复其myd\frm数据文件,所有数据恢复成功。
[其他]
1、Linux Ext3数据删除后应尽快断掉文件系统IO,通常umount文件系统即可。
2、对故障卷做dd备份,,确保数据恢复过程不会导致更严重的故障。
版权声明:原创作品,允许转载,转载时请务必以超链接形式标明文章 原始出处 、作者信息和本声明。否则将追究法律责任。
作者:张宇,北亚MYSQL数据恢复中心,转载请联系作者,如果实在不想联系作者,至少请保留版权,谢谢。

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