记一次使用ASMLIB标记磁盘导致的数据库系统宕机案例

本文主要是介绍记一次使用ASMLIB标记磁盘导致的数据库系统宕机案例，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

在对某医院HIS数据库环境搜集过程中，发现这套Oracle RAC数据库没有正确使用到multipath提供的多路径磁盘，本着对用户及合作伙伴负责的态度，将过程做一描述说明，以及提出一点解决问题的思路建议。

系统环境：

操作系统为Linux

数据库Oracle 19c

采用ASMLIB创建共享磁盘查看相关信息如下(仅以DATA01为例)：

执行multipath -ll命令返回如下

DATA01 (3600507680c80833288000000000000ca) dm-3 IBM   ,2145      
size=500G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:0 sdb       8:16 active ready running
|- 16:0:0:0 sdae       65:224 active ready running
|- 7:0:1:0 sdi       8:128 active ready running
|- 16:0:2:0 sdas       66:192 active ready running
|- 7:0:2:0 sdp       8:240 active ready running
|- 16:0:3:0 sdar       66:176 active ready running
|- 7:0:3:0 sdw       65:96 active ready running
`- 16:0:1:0 sdad       65:208 active ready running
OCR03 (3600507680c80833288000000000000e3) dm-9 IBM   ,2145      
size=5.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:6 sdh       8:112 active ready running
|- 16:0:0:6 sdak       66:64 active ready running
|- 7:0:1:6 sdo       8:224 active ready running
|- 16:0:2:6 sday       67:32 active ready running
|- 7:0:2:6 sdv       65:80 active ready running
|- 16:0:3:6 sdbe       67:128 active ready running
|- 7:0:3:6 sdac       65:192 active ready running
`- 16:0:1:6 sdaq       66:160 active ready running
OCR02 (3600507680c80833288000000000000e2) dm-8 IBM   ,2145      
size=5.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:5 sdg       8:96 active ready running
|- 16:0:0:5 sdaj       66:48 active ready running
|- 7:0:1:5 sdn       8:208 active ready running
|- 16:0:2:5 sdax       67:16 active ready running
|- 7:0:2:5 sdu       65:64 active ready running
|- 16:0:3:5 sdbd       67:112 active ready running
|- 7:0:3:5 sdab       65:176 active ready running
`- 16:0:1:5 sdap       66:144 active ready running
OCR01 (3600507680c80833288000000000000e1) dm-7 IBM   ,2145      
size=5.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:4 sdf       8:80 active ready running
|- 16:0:0:4 sdai       66:32 active ready running
|- 7:0:1:4 sdm       8:192 active ready running
|- 16:0:2:4 sdaw       67:0 active ready running
|- 7:0:2:4 sdt       65:48 active ready running
|- 16:0:3:4 sdbc       67:96 active ready running
|- 7:0:3:4 sdaa       65:160 active ready running
`- 16:0:1:4 sdao       66:128 active ready running
DATA04 (3600507680c80833288000000000000cd) dm-6 IBM   ,2145      
size=500G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:3 sde       8:64 active ready running
|- 16:0:0:3 sdah       66:16 active ready running
|- 7:0:1:3 sdl       8:176 active ready running
|- 16:0:2:3 sdav       66:240 active ready running
|- 7:0:2:3 sds       65:32 active ready running
|- 16:0:3:3 sdbb       67:80 active ready running
|- 7:0:3:3 sdz       65:144 active ready running
`- 16:0:1:3 sdan       66:112 active ready running
DATA03 (3600507680c80833288000000000000cc) dm-5 IBM   ,2145      
size=500G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:2 sdd       8:48 active ready running
|- 16:0:0:2 sdag       66:0 active ready running
|- 7:0:1:2 sdk       8:160 active ready running
|- 16:0:2:2 sdau       66:224 active ready running
|- 7:0:2:2 sdr       65:16 active ready running
|- 16:0:3:2 sdba       67:64 active ready running
|- 7:0:3:2 sdy       65:128 active ready running
`- 16:0:1:2 sdam       66:96 active ready running
DATA02 (3600507680c80833288000000000000cb) dm-4 IBM   ,2145      
size=500G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=30 status=active
|- 7:0:0:1 sdc       8:32 active ready running
|- 16:0:0:1 sdaf       65:240 active ready running
|- 7:0:1:1 sdj         8:144 active ready running
|- 16:0:2:1 sdat       66:208 active ready running
|- 7:0:2:1 sdq       65:0 active ready running
|- 16:0:3:1 sdaz       67:48 active ready running
|- 7:0:3:1 sdx         65:112 active ready running
`- 16:0:1:1 sdal       66:80 active ready running

查看multipath.conf配置文件

defaults {
polling_interval 10
path_selector   "round-robin 0"
path_grouping_policy multibus
uid_attribute   ID_SERIAL
prio     alua
path_checker   readsector0
rr_min_io   100
max_fds     8192
rr_weight   priorities
failback   immediate
no_path_retry   fail
user_friendly_names yes
}
multipaths {
multipath {      wwid     3600507680c80833288000000000000caalias     DATA01path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000cbalias     DATA02path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000ccalias     DATA03path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000cdalias     DATA04path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000e1alias     OCR01path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000e2alias     OCR02path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
multipath {wwid     3600507680c80833288000000000000e3alias     OCR03path_grouping_policy multibuspath_selector   "round-robin 0"failback   manualrr_weight   prioritiesno_path_retry   5
}
}
blacklist {
wwid 36f4ee08029ce6e002a007008d5711e3b
}

查看ASM信息

col path for a30
col name for a10
set line 300
SQL> select mode_status,name,state,path from v$asm_disk;
MODE_STATUS     NAME   STATE       PATH
--------------------- ---------- ------------------------ ---------------------------
ONLINE       OCR_0000 NORMAL     /dev/oracleasm/disks/OCR01
ONLINE       OCR_0001 NORMAL     /dev/oracleasm/disks/OCR02
ONLINE       OCR_0002 NORMAL     /dev/oracleasm/disks/OCR03
ONLINE       DATA_0003 NORMAL     /dev/oracleasm/disks/DATA04
ONLINE       DATA_0002 NORMAL     /dev/oracleasm/disks/DATA03
ONLINE       DATA_0001 NORMAL     /dev/oracleasm/disks/DATA02
ONLINE       DATA_0000 NORMAL     /dev/oracleasm/disks/DATA01
7 rows selected.
SQL> show parameter asm_disk
NAME         TYPE         VALUE
------------------------------------ --------------------------------- ------------
asm_diskgroups       string         DATA
asm_diskstring       string         /dev/oracleasm/disks/*

可以看到，8个盘的标签都是DATA01,其中sdb、sdi、sdp、sdw、sdae、sdar、sdas、sdad为单路径，8个路径绑定成了DATA01，当前正使⽤着[8, 16]这个设备，这个设备为sdb。

查看设备的主设备号和次设备号，看这个设备是对应到/dev/目录下的那个设备时，发现/dev/oracleasm/disks下面的盘不是对应到/dev/dm-xx盘，由此基本确定了asmlib没有使用多路径的盘。

ASMLIB包的基本原理是对盘起一个名字，如“DATA01”然后把这个名字存入磁盘的内容的头部。下次机器自动启动时，会自动运行/etc/rc.d/init.d/oracleasm　start，这时会自动扫描硬盘，扫描过程中，是会读前面我们写入名称，由于使用了多路径，那么在/dev/下会有几个设备名对应着同一个硬盘，其中/dev/sdxxx的是各个路径盘，/dev/dm-xx是把这些路径合并了一个盘，正常情况下oracle会要求ASMLIB使用/dev/dm-xx盘，但ASMLIB的扫描规则是使用最先扫描到的盘，后面再扫描到的设备，只要上面的名称与前面相同，就使用前面的设备名，不管再次扫描到的了。由此极有可能导致链路宕掉随之而来ASM卷组盘也掉了，进而引发数据文件损坏或者宕机。其实oracle的官方网站也说明了此问题。

Metalink Note<How To Setup ASM & ASMLIB On Native Linux Multipath Mapper disks?

[ID 602952.1]

ASMLIB Installation & Configuration On MultiPath Mapper Devices (Step by Step Demo) On RAC Or Standalone Configurations. (文档 ID 1594584.1)

建议修改/etc/sysconfig/oracleasm（oracleasm-_dev_oracleasm）配置文中ORACLEASM_SCANORDER及ORACLEASM_SCANEXCLUDE，以便ASMLIB能找到正确的设备文件

Configure ASMLIB to use multipath (from each node on RAC environments):

By any path the ASMLIB can found the disks, but, the best path is using the multipath :

Modify in /etc/sysconfig/oracleasm :
ORACLEASM_SCANORDER=”dm”
ORACLEASM_SCANEXCLUDE=”sd”

note: The Oracle ASMLib configuration file is located at /etc/sysconfig/oracleasm. It is a link to file /etc/sysconfig/oracleasm-_dev_oracleasm.

Restart ASMLIB (from each node on RAC environments):
/etc/init.d/oracleasm stop
/etc/init.d/oracleasm start

参考链接:

http://www.help2ora.com/index.php/2011/08/16/how-to-setup-asm-asmlib-on-native-linux-multipath-mapper-disks/

https://www.oracle.com/linux/technologies/multipath-disks.html

如有可能尽量采用udev绑定，因为Oracle官方也建议RedHat/OLE 5以上建议采用udev。因为采用ASMLIB包的形式，只要Linux Kernel更新，都需要替换新的ASMLIB包，这就意味着ASMLIB需要花费时间去维护，同时可能引入未知的Bug。

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