Home Database Mysql Tutorial ext3下删除mysql数据库的数据恢复案例_MySQL

ext3下删除mysql数据库的数据恢复案例_MySQL

Jun 01, 2016 pm 02:02 PM
ext3 mysql Data Recovery

数据恢复

    [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。

 

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