惜分飞

从版本12.1开始，ASM会对某些物理元数据做一份复制，具体的说是每个磁盘的第一个AU（0号AU）上元数据。这意味着，ASM同时维护着两份磁盘头、FST（Free Space Table）表、AT（Allocation table）表的数据。需要注意的是ASM对这些数据采用的是复制（replicate），而不是镜像（mirror）。ASM镜像（mirror）意味着把一份数据，拷贝到不同磁盘上；而物理元数据的副本位于相同的磁盘，因此使用的术语复制（replicate）。这意味着在external冗余的磁盘组中，物理元数据也会被复制。PST也是物理元数据，但是ASM是通过镜像，而不是复制来提供数据保护。因此只有在normal和high冗余的磁盘组中，PST表存在数据的冗余。物理元数据位于每块ASM磁盘的0号AU。元数据复制的特性打开后，ASM会把0号AU的内容拷贝到11号AU，然后同时维护这两份副本。创建磁盘组时如果指定或修改了一个已经存在的磁盘组的compatibility属性为12.1及以上，该特性会自动被打开。当提升ASM compatibility属性值为12.1及以上时，如果11号AU有数据，ASM将把这些数据移动到别处，然后将物理元数据复制到11号AU。从版本11.1.0.7开始，ASM在1号AU的倒数第二个块维护了一份磁盘头的副本。在版本12.1中，ASM仍然维护着这个副本数据。也就是说，现在每个ASM磁盘，有磁盘头的三个副本。
au 0中具体数据

[grid@localhost ~]$ sqlplus / as sysasm

SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 22 08:13:31 2017

Copyright (c) 1982, 2016, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> create diskgroup xifenfei  external redundancy disk '/dev/xifenfei-sdg','/dev/xifenfei-sdh';

Diskgroup created.

SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

查看xifenfei磁盘组属性

[grid@localhost ~]$ asmcmd lsattr -l -G XIFENFEI
Name                     Value       
access_control.enabled   FALSE       
access_control.umask     066         
au_size                  1048576     
cell.smart_scan_capable  FALSE       
compatible.asm           11.2.0.2.0  
compatible.rdbms         10.1.0.0.0  
disk_repair_time         3.6h        
idp.boundary             auto        
idp.type                 dynamic     
sector_size              512        

这里可以看到目前compatible.asm为11.2,没有phys_meta_replicated属性

查看磁盘头信息
ASM磁盘头的fdhdb.flags条目指代了物理元数据的复制状态：
· kfdhdb.flags = 0 — 元数据没有复制
· kfdhdb.flags = 1 — 元数据已经复制完毕
· kfdhdb.flags = 2 — 元数据在复制过程中

[grid@localhost ~]$ for disk in `asmcmd lsdsk -G XIFENFEI --suppressheader`; 
> do kfed read $disk | egrep "dskname|flags"; done
kfdhdb.dskname:           XIFENFEI_0000 ; 0x028: length=13
kfdhdb.flags:                         0 ; 0x0fc: 0x00000000
kfdhdb.dskname:           XIFENFEI_0001 ; 0x028: length=13
kfdhdb.flags:                         0 ; 0x0fc: 0x00000000

[grid@localhost ~]$ kfed read /dev/xifenfei-sdg|grep kfbh.type
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg aun=11|grep kfbh.type
kfbh.type:                            8 ; 0x002: KFBTYP_CHNGDIR
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg blkn=254 aun=1|grep kfbh.type
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD

这里也比较明显,在aun 11的位置没有第一个au的备份
修改compatible.asm为12.2

[grid@localhost ~]$  asmcmd setattr -G XIFENFEI compatible.asm 12.2.0.0.0
[grid@localhost ~]$ asmcmd lsattr -l -G XIFENFEI
Name                        Value         
access_control.enabled      FALSE         
access_control.umask        066           
appliance._partnering_type  NULL          
au_size                     1048576       
cell.smart_scan_capable     FALSE         
cell.sparse_dg              allnonsparse  
compatible.asm              12.2.0.0.0    
compatible.rdbms            10.1.0.0.0    
content.check               FALSE         
content.type                data          
disk_repair_time            3.6h          
failgroup_repair_time       24.0h         
idp.boundary                auto          
idp.type                    dynamic       
logical_sector_size         512           
phys_meta_replicated        true          
preferred_read.enabled      FALSE         
scrub_async_limit           1             
scrub_metadata.enabled      FALSE         
sector_size                 512           
thin_provisioned            FALSE         

这里可以看到修改为compatible.asm=12.2之后，出现phys_meta_replicated属性

查看au的备份

[grid@localhost ~]$ for disk in `asmcmd lsdsk -G XIFENFEI --suppressheader`;
> do kfed read $disk | egrep "dskname|flags"; done
kfdhdb.dskname:           XIFENFEI_0000 ; 0x028: length=13
kfdhdb.flags:                         1 ; 0x0fc: 0x00000001
kfdhdb.dskname:           XIFENFEI_0001 ; 0x028: length=13
kfdhdb.flags:                         1 ; 0x0fc: 0x00000001

[grid@localhost ~]$ kfed read /dev/xifenfei-sdg aun=11|grep kfbh.type
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg blkn=254 aun=1|grep kfbh.type
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg|grep kfbh.type
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD

这里就可以看到kfdhdb.flags为1，在au 11的地方也变为了磁盘头信息

模拟第一个au彻底损坏

[grid@localhost ~]$ dd if=/dev/zero of=/dev/xifenfei-sdg bs=1024k count=1 conv=notrunc 
1+0 records in
1+0 records out
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg
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]

尝试mount磁盘组

SQL> alter diskgroup xifenfei mount;
alter diskgroup xifenfei mount
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15017: diskgroup "XIFENFEI" cannot be mounted
ORA-15040: diskgroup is incomplete

alert日志信息

SQL> alter diskgroup xifenfei mount
2017-04-22T08:30:00.889037-04:00
NOTE: cache registered group XIFENFEI 1/0xB15C368B
NOTE: cache began mount (first) of group XIFENFEI 1/0xB15C368B
NOTE: Assigning number (1,1) to disk (/dev/xifenfei-sdh)
2017-04-22T08:30:01.001544-04:00
ERROR: no read quorum in group: required 1, found 0 disks
2017-04-22T08:30:01.001737-04:00
NOTE: cache dismounting (clean) group 1/0xB15C368B (XIFENFEI)
NOTE: messaging CKPT to quiesce pins Unix process pid: 20894, image: oracle@localhost.localdomain (TNS V1-V3)
NOTE: dbwr not being msg'd to dismount
NOTE: LGWR not being messaged to dismount
NOTE: cache dismounted group 1/0xB15C368B (XIFENFEI)
NOTE: cache ending mount (fail) of group XIFENFEI number=1 incarn=0xb15c368b
NOTE: cache deleting context for group XIFENFEI 1/0xb15c368b
2017-04-22T08:30:01.028825-04:00
GMON dismounting group 1 at 2 for pid 23, osid 20894
2017-04-22T08:30:01.029146-04:00
NOTE: Disk XIFENFEI_0001 in mode 0x8 marked for de-assignment
ERROR: diskgroup XIFENFEI was not mounted
ORA-15032: not all alterations performed
ORA-15017: diskgroup "XIFENFEI" cannot be mounted
ORA-15040: diskgroup is incomplete

2017-04-22T08:30:01.036014-04:00
ERROR: alter diskgroup xifenfei mount

很明显由于xifenfei-sdg第一个au 已经被完全dd掉，xifenfei磁盘组无法mount，提示ORA-15040: diskgroup is incomplete

使用备份au还原

[grid@localhost ~]$ dd if=/dev/xifenfei-sdg skip=11 bs=1024k count=1 of=/tmp/sdg_header
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.048576 s, 21.6 MB/s

[grid@localhost ~]$ kfed read /tmp/sdg_header |more
kfbh.endian:                          1 ; 0x000: 0x01
kfbh.hard:                          130 ; 0x001: 0x82
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD
kfbh.datfmt:                          2 ; 0x003: 0x02
kfbh.block.blk:                       0 ; 0x004: blk=0
kfbh.block.obj:              2147483648 ; 0x008: disk=0
kfbh.check:                  3085718230 ; 0x00c: 0xb7ec52d6
kfbh.fcn.base:                       41 ; 0x010: 0x00000029
kfbh.fcn.wrap:                        0 ; 0x014: 0x00000000
kfbh.spare1:                          0 ; 0x018: 0x00000000
kfbh.spare2:                          0 ; 0x01c: 0x00000000
kfdhdb.driver.provstr:         ORCLDISK ; 0x000: length=8
kfdhdb.driver.reserved[0]:            0 ; 0x008: 0x00000000
kfdhdb.driver.reserved[1]:            0 ; 0x00c: 0x00000000
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:                203423744 ; 0x020: 0x0c200000
kfdhdb.dsknum:                        0 ; 0x024: 0x0000
kfdhdb.grptyp:                        1 ; 0x026: KFDGTP_EXTERNAL
kfdhdb.hdrsts:                        3 ; 0x027: KFDHDR_MEMBER
kfdhdb.dskname:           XIFENFEI_0000 ; 0x028: length=13
kfdhdb.grpname:                XIFENFEI ; 0x048: length=8
kfdhdb.fgname:            XIFENFEI_0000 ; 0x068: length=13
[grid@localhost ~]$ dd if=/tmp/sdg_header of=/dev/xifenfei-sdg bs=1024k count=1 conv=notrunc
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0262761 s, 39.9 MB/s
[grid@localhost ~]$ kfed read /dev/xifenfei-sdg|more
kfbh.endian:                          1 ; 0x000: 0x01
kfbh.hard:                          130 ; 0x001: 0x82
kfbh.type:                            1 ; 0x002: KFBTYP_DISKHEAD
kfbh.datfmt:                          2 ; 0x003: 0x02
kfbh.block.blk:                       0 ; 0x004: blk=0
kfbh.block.obj:              2147483648 ; 0x008: disk=0
kfbh.check:                  3085718230 ; 0x00c: 0xb7ec52d6
kfbh.fcn.base:                       41 ; 0x010: 0x00000029
kfbh.fcn.wrap:                        0 ; 0x014: 0x00000000
kfbh.spare1:                          0 ; 0x018: 0x00000000
kfbh.spare2:                          0 ; 0x01c: 0x00000000
kfdhdb.driver.provstr:         ORCLDISK ; 0x000: length=8
kfdhdb.driver.reserved[0]:            0 ; 0x008: 0x00000000
kfdhdb.driver.reserved[1]:            0 ; 0x00c: 0x00000000
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:                203423744 ; 0x020: 0x0c200000
kfdhdb.dsknum:                        0 ; 0x024: 0x0000
kfdhdb.grptyp:                        1 ; 0x026: KFDGTP_EXTERNAL
kfdhdb.hdrsts:                        3 ; 0x027: KFDHDR_MEMBER
kfdhdb.dskname:           XIFENFEI_0000 ; 0x028: length=13
kfdhdb.grpname:                XIFENFEI ; 0x048: length=8
kfdhdb.fgname:            XIFENFEI_0000 ; 0x068: length=13

xifenfei磁盘组mount成功

[grid@localhost ~]$ sqlplus / as sysasm

SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 22 08:34:53 2017

Copyright (c) 1982, 2016, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> alter diskgroup xifenfei mount;

Diskgroup altered.

asm alert日志

SQL> alter diskgroup xifenfei mount
2017-04-22T08:34:59.298838-04:00
NOTE: cache registered group XIFENFEI 1/0xFA6C368E
NOTE: cache began mount (first) of group XIFENFEI 1/0xFA6C368E
NOTE: Assigning number (1,0) to disk (/dev/xifenfei-sdg)
NOTE: Assigning number (1,1) to disk (/dev/xifenfei-sdh)
2017-04-22T08:35:05.447528-04:00
NOTE: GMON heartbeating for grp 1 (XIFENFEI)
GMON querying group 1 at 5 for pid 23, osid 21195
2017-04-22T08:35:05.449557-04:00
NOTE: cache is mounting group XIFENFEI created on 2017/04/22 08:13:39
NOTE: cache opening disk 0 of grp 1: XIFENFEI_0000 path:/dev/xifenfei-sdg
NOTE: 04/22/17 08:35:04 XIFENFEI.F1X0 found on disk 0 au 2 fcn 0.0 datfmt 2
NOTE: cache opening disk 1 of grp 1: XIFENFEI_0001 path:/dev/xifenfei-sdh
2017-04-22T08:35:05.450316-04:00
NOTE: cache mounting (first) external redundancy group 1/0xFA6C368E (XIFENFEI)
NOTE: cache recovered group 1 to fcn 0.352
NOTE: redo buffer size is 256 blocks (1056768 bytes)
2017-04-22T08:35:05.504356-04:00
NOTE: LGWR attempting to mount thread 1 for diskgroup 1 (XIFENFEI)
NOTE: LGWR found thread 1 closed at ABA 2.63 lock domain=0 inc#=0 instnum=1
NOTE: LGWR mounted thread 1 for diskgroup 1 (XIFENFEI)
2017-04-22T08:35:05.555647-04:00
NOTE: LGWR opened thread 1 (XIFENFEI) at fcn 0.352 ABA 3.64 lock domain=1 inc#=0 instnum=1 
  gx.incarn=4201395854 mntstmp=2017/04/22 08:35:05.510000
2017-04-22T08:35:05.556006-04:00
NOTE: cache mounting group 1/0xFA6C368E (XIFENFEI) succeeded
NOTE: cache ending mount (success) of group XIFENFEI number=1 incarn=0xfa6c368e
2017-04-22T08:35:05.596616-04:00
NOTE: Instance updated compatible.asm to 12.2.0.0.0 for grp 1 (XIFENFEI).
2017-04-22T08:35:05.599181-04:00
NOTE: Instance updated compatible.rdbms to 10.1.0.0.0 for grp 1 (XIFENFEI).
2017-04-22T08:35:05.608332-04:00
SUCCESS: diskgroup XIFENFEI was mounted
2017-04-22T08:35:05.635588-04:00
SUCCESS: alter diskgroup xifenfei mount