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Oracle rAC asm备份元数据之md_backup和md_restore好处与坏处

在11g的asm中增加了md_backup和md_restore命令,用来备份和还原asm的元数据信息

查看当前Oracle ASM磁盘组相关信息

SQL> select PATH,b.NAME from v$asm_disk a,v$asm_diskgroup b where a.GROUP_NUMBER=b.GROUP_NUMBER;

PATH NAME

---------------------------------------- ----------

/dev/oracleasm/disks/VOL2 DATA

/dev/oracleasm/disks/VOL1 DATA

/dev/oracleasm/disks/VOL4 XIFENFEI

/dev/oracleasm/disks/VOL3 XIFENFEI

Oracle RAC 使用md_backup备份磁盘组

--备份所有mount磁盘组

ASMCMD> md_backup /tmp/xifenfei.md

Disk group metadata to be backed up: DATA

Disk group metadata to be backed up: XIFENFEI

Current alias directory path: XFF/ARCHIVELOG

Current alias directory path: XFF/ARCHIVELOG/2012_04_30

Current alias directory path: XFF/ONLINELOG

Current alias directory path: rac-cluster/OCRFILE

Current alias directory path: XFF/ARCHIVELOG/2012_05_01

Current alias directory path: XFF/CONTROLFILE

Current alias directory path: XFF/ARCHIVELOG/2012_04_13

Current alias directory path: rac-cluster/ASMPARAMETERFILE

Current alias directory path: rac-cluster

Current alias directory path: XFF

Current alias directory path: XFF/ARCHIVELOG/2012_03_03

Current alias directory path: XFF/PARAMETERFILE

Current alias directory path: XFF/DATAFILE

Current alias directory path: ASM/DATAFILE

Current alias directory path: XFF/CONTROLFILE

Current alias directory path: XFF

Current alias directory path: XFF/ONLINELOG

Current alias directory path: XFF/TEMPFILE

Current alias directory path: ASM

--备份指定磁盘组

ASMCMD> md_backup /tmp/xifenfei_data.md -G DATA

Disk group metadata to be backed up: DATA

Current alias directory path: XFF/ARCHIVELOG/2012_03_03

Current alias directory path: XFF/CONTROLFILE

Current alias directory path: XFF/ARCHIVELOG/2012_05_01

Current alias directory path: XFF/ARCHIVELOG

Current alias directory path: rac-cluster/OCRFILE

Current alias directory path: XFF/ARCHIVELOG/2012_05_24

Current alias directory path: XFF/ONLINELOG

Current alias directory path: XFF/ARCHIVELOG/2012_04_30

Current alias directory path: rac-cluster/ASMPARAMETERFILE

Current alias directory path: rac-cluster

Current alias directory path: XFF

Current alias directory path: XFF/ARCHIVELOG/2012_04_13

Oracle RAC 使用md_restore恢复磁盘组

--生产sql文件(未执行)

ASMCMD> md_restore -S /tmp/get_dg_sql -G data /tmp/xifenfei_data.md

Current Diskgroup metadata being restored: DATA

破坏XIFENFEI磁盘组中的其中一个asm disk(/dev/oracleasm/disks/VOL3)

[root@rac1 tmp]# dd if=/dev/zero of=/dev/sdb1 bs=4096 count=1

1+0 records in

1+0 records out

4096 bytes (4.1 kB) copied, 4.8629e-05 seconds, 84.2 MB/s

--尝试还原磁盘组(操作单位是磁盘组)

ASMCMD> md_restore /tmp/xifenfei.md --silent -G xifenfei

Current Diskgroup metadata being restored: XIFENFEI

ASMCMD-9352: CREATE DISKGROUP failed

ORA-15018: diskgroup cannot be created

ORA-15033: disk /dev/oracleasm/disks/VOL4 belongs to diskgroup "XIFENFEI" (DBD ERROR: OCIStmtExecute)

--如果一个磁盘组中某个asm disk 出了问题,这种方法不能生效,甚至需要先dd 处理掉所有该磁盘组中的asm disk

Oracle研究中心总结说明

md_backup和md_restore是磁盘组级别的备份和还原,如果一个磁盘组的某个asm disk出现问题,使用这对命令解决起来还是很麻烦,甚至根本不可行(因为代价太大:要删除该磁盘组其他asm disk header,然后要重新还原所有数据文件),这样的情景下dd或者kfed的备份还是非常有必要.如果是一个磁盘组都损坏,需要还原磁盘组,这个时候这个命令非常的完美(至少比起dd和kfed方便很多).md_backup/md_restore和dd与kfed是互补的命令,而不是md_backup/md_restore出现使得dd和kfed在asm元数据的备份恢复上就没有用武之地.

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