本文档提供一个关于ASM磁盘头数据被修复的例子。
ASM磁盘头（前4K）的副本存在于10.2.0.5、11.1.0.7、11.2及以后的版本中。它可用于尝试还原有效的ASM磁盘头（假设只有磁盘的前4k受到影响/覆盖）。要还原ASM磁盘头（假设自动ASM磁盘头备份状态良好），请执行以下步骤：
备份该磁盘前52M数据
[grid@dbaasm ~]$ dd if=/dev/oracleasm/disks/ASMDISK2 of=/tmp/ASMDISK2.dump bs=1048576 count=50 50+0 records in 50+0 records out 52428800 bytes (52 MB) copied, 0.667474 seconds, 78.5 MB/s
收集分配单元大小(kfdhdb.ausize公司)来自另一个正常磁盘成员（来自同一受影响的磁盘组）：
[grid@dbaasm ~]$ kfed read /dev/oracleasm/disks/ASMDISK1 | egrep 'ausize|dsknum|dskname|grpname|fgname' kfdhdb.dsknum: 0 ; 0x024: 0x0000 kfdhdb.dskname: ASMDISK1 ; 0x028: length=8 kfdhdb.grpname: DATA ; 0x048: length=4 kfdhdb.fgname: FG1_SAN1 ; 0x068: length=8 kfdhdb.ausize: 2097152 ; 0x0bc: 0x00200000
修复ASMDISK2
[grid@dbaasm ~]$ kfed repair /dev/oracleasm/disks/ASMDISK2 ausz=2097152
验证：
[grid@dbaasm ~]$ kfed read /dev/oracleasm/disks/ASMDISK2 | head -40 kfbh.endian: 1 ; 0x000: 0x01 kfbh.hard: 130 ; 0x001: 0x82 kfbh.type: 1 ; 0x002: KFBTYP_DISKHEAD kfbh.datfmt: 1 ; 0x003: 0x01 kfbh.block.blk: 0 ; 0x004: blk=0 kfbh.block.obj: 2147483650 ; 0x008: disk=2 kfbh.check: 4052202307 ; 0x00c: 0xf187b343 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 kfdhdb.driver.provstr: ORCLDISKASMDISK2 ; 0x000: length=16 kfdhdb.driver.reserved[0]: 1145918273 ; 0x008: 0x444d5341 kfdhdb.driver.reserved[1]: 843797321 ; 0x00c: 0x324b5349 kfdhdb.driver.reserved[2]: 0 ; 0x010: 0x00000000 kfdhdb.driver.reserved[3]: 0 ; 0x014: 0x00000000 kfdhdb.driver.reserved[4]: 0 ; 0x018: 0x00000000 kfdhdb.driver.reserved[5]: 0 ; 0x01c: 0x00000000 kfdhdb.compat: 186647296 ; 0x020: 0x0b200300 kfdhdb.dsknum: 2 ; 0x024: 0x0002 kfdhdb.grptyp: 2 ; 0x026: KFDGTP_NORMAL kfdhdb.hdrsts: 3 ; 0x027: KFDHDR_MEMBER kfdhdb.dskname: ASMDISK2 ; 0x028: length=8 kfdhdb.grpname: DATA ; 0x048: length=4 kfdhdb.fgname: FG2_SAN2 ; 0x068: length=8 kfdhdb.capname: ; 0x088: length=0 kfdhdb.crestmp.hi: 32974423 ; 0x0a8: HOUR=0x17 DAYS=0x12 MNTH=0x9 YEAR=0x7dc kfdhdb.crestmp.lo: 1180930048 ; 0x0ac: USEC=0x0 MSEC=0xe4 SECS=0x26 MINS=0x11 kfdhdb.mntstmp.hi: 33003184 ; 0x0b0: HOUR=0x10 DAYS=0x15 MNTH=0x5 YEAR=0x7de kfdhdb.mntstmp.lo: 1230240768 ; 0x0b4: USEC=0x0 MSEC=0xff SECS=0x15 MINS=0x12 kfdhdb.secsize: 512 ; 0x0b8: 0x0200 kfdhdb.blksize: 4096 ; 0x0ba: 0x1000 kfdhdb.ausize: 2097152 ; 0x0bc: 0x00200000 kfdhdb.mfact: 228480 ; 0x0c0: 0x00037c80 kfdhdb.dsksize: 9769 ; 0x0c4: 0x00002629 kfdhdb.pmcnt: 2 ; 0x0c8: 0x00000002 kfdhdb.fstlocn: 1 ; 0x0cc: 0x00000001 kfdhdb.altlocn: 2 ; 0x0d0: 0x00000002 kfdhdb.f1b1locn: 0 ; 0x0d4: 0x00000000 kfdhdb.redomirrors[0]: 0 ; 0x0d8: 0x0000 .
mount：
alter diskgroup DATA mount;
注意：
只有受影响磁盘的前4K被覆盖/擦除/重叠 -- asm磁盘中只备份了那点数据，如果损坏较多，无法恢复，且还原力度较大
ASM磁盘头备份状态良好
坏的磁盘头信息：
[grid@dbaasm ~]$ kfed read /dev/oracleasm/disks/ASMDISK2 kfbh.endian: 0 ; 0x000: 0x00 kfbh.hard: 0 ; 0x001: 0x00 kfbh.type: 0 ; 0x002: KFBTYP_INVALID kfbh.datfmt: 0 ; 0x003: 0x00 kfbh.block.blk: 0 ; 0x004: blk=0 kfbh.block.obj: 0 ; 0x008: file=0 kfbh.check: 0 ; 0x00c: 0x00000000 kfbh.fcn.base: 0 ; 0x010: 0x00000000 kfbh.fcn.wrap: 0 ; 0x014: 0x00000000 kfbh.spare1: 0 ; 0x018: 0x00000000 kfbh.spare2: 0 ; 0x01c: 0x00000000 000000000 00000000 00000000 00000000 00000000 [................] Repeat 255 times KFED-00322: Invalid content encountered during block traversal: [kfbtTraverseBlock][Invalid OSM block type][][0]
磁盘头备份规则：
AU SIZE : 备份块:
1 M 510
2 M 1022
4M 2046
8M 4094
16M 8190
32M 16382
64M 32766