oracle+磁盘挂载格式化,oracle asm disk格式化恢复—格式化为ext4文件系统
昨天中午接到一位朋友紧急求救电话,大概场景如下,asm data磁盘组一共把个asm disk,但是使用4个lun实现的(也就是说每个lun使用fdisk进行分区),该主机上还有一个lun是用来存放备份的挂载在/xifenfei目录.客户记得他们的/xifenfei目录是/dev/sdh1这个分区,上次主机重启之后,rac工作正常,但是/xifenfei这个目录对应的/dev/sdh1无法挂载上去(提示无法找到超级块).然后我这位朋友上去也不管三七二一直接执行了mkfs.ext4 /dev/sdh1.结果整个asm 磁盘组异常了.最后他通过fdisk命令一看发现完蛋了,以前的/dev/sdh 已经变为了/dev/sdc,而现在的/dev/sdh是以前的asm disk.也就是说,他把asm 磁盘组中的一个disk进行了格式化为ext4文件系统操作.
ext4文件系统大概结构
通过这里大概可以发现在格式化为ext4文件系统并非把所有的磁盘数据全部重写主要就是覆盖一些ext4必要的一些元数据信息,理论上没有覆盖部分的数据依旧可以恢复
fdisk 分析现在磁盘情况
[root@db3 ~]# fdisk -l
Disk /dev/sda: 171.8 GB, 171798691840 bytes
255 heads, 63 sectors/track, 20886 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00055b12
Device Boot Start End Blocks Id System
/dev/sda1 * 1 64 512000 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 64 8223 65536000 82 Linux swap / Solaris
/dev/sda3 8223 20887 101723136 8e Linux LVM
Disk /dev/sdb: 751.6 GB, 751619276800 bytes
255 heads, 63 sectors/track, 91379 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00b6888f
Device Boot Start End Blocks Id System
/dev/sdb1 1 91379 734001786 5 Extended
/dev/sdb5 1 15000 120487437 83 Linux
Disk /dev/sdd: 1073 MB, 1073741824 bytes
34 heads, 61 sectors/track, 1011 cylinders
Units = cylinders of 2074 * 512 = 1061888 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00083b68
Device Boot Start End Blocks Id System
Disk /dev/sdf: 526.1 GB, 526133493760 bytes
255 heads, 63 sectors/track, 63965 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000c10d8
Device Boot Start End Blocks Id System
/dev/sdf1 1 13054 104856223+ 83 Linux
/dev/sdf2 13055 63965 408942607+ 83 Linux
Disk /dev/sde: 1073 MB, 1073741824 bytes
34 heads, 61 sectors/track, 1011 cylinders
Units = cylinders of 2074 * 512 = 1061888 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b120f
Device Boot Start End Blocks Id System
Disk /dev/sdc: 1795.3 GB, 1795296329728 bytes
255 heads, 63 sectors/track, 218265 cylinders
Units = cylinders of 16065 * 512 = 822