Oracle RAC 搭建——使用多路径（Multipath）

原文地址：http://blog.163.com/donfang_jianping/blog/static/136473951201410228567115/

在

http://blog.163.com/donfang_jianping/blog/static/136473951201311111384468/，http://blog.163.com/donfang_jianping/blog/static/136473951201311712517496/，http://blog.163.com/donfang_jianping/blog/static/13647395120131179581321/，http://blog.163.com/donfang_jianping/blog/static/136473951201311615737245/中，我们介绍了Oracle RAC完整的一个搭建过程。这里我们来看一下使用多路径来建立ASM的存储。

LInux多路径技术通常用在FC存储环境下，当然了，在ISCSI下也可以使用。这里我没有太多的介绍多路径，其实，在实际的使用当中，多数是采用默认。最多就是为每一个wwid配置一个别名，把不必要的设备加入黑名单（比如有/boot分区的设备），有时候会根据磁头与HBA卡的配置，把 path_grouping_policy改为failover。关于更多的多路径的介绍，大家可以看“Red_Hat_Enterprise_Linux-6-DM_Multipath-zh-CN.pdf”这本电子书。

下面，我们以iscsi存储环境为例，来看一下具体如何使用。

其他的步骤一样，也就是说，在http://blog.163.com/donfang_jianping/blog/static/13647395120131179581321/中的“ASM磁盘组的配置”这一步，我们不需要安装oracleasm-2.6.18-194.el5-2.0.5-1.el5.x86_64,

oracleasmlib-2.0.4-1.el5.x86_64，

oracleasm-support-2.1.8-1.el5.x86_64这些rpm包，也需要对ISCSI挂载的共享磁盘进行分区；我们可以直接使用多路径这个技术。

在ISCSI磁盘挂载完成以后，我们来进行对多路径进行配置。具体步骤如下：

（1）程序包的安装。

在redhat 6.5当中，我们需要安装如下的程序包，

device-mapper-multipath-libs-0.4.9-72.el6.x86_64

device-mapper-persistent-data-0.2.8-2.el6.x86_64

device-mapper-multipath-0.4.9-72.el6.x86_64

device-mapper-libs-1.02.79-8.el6.x86_64

device-mapper-event-1.02.79-8.el6.x86_64

device-mapper-1.02.79-8.el6.x86_64

device-mapper-event-libs-1.02.79-8.el6.x86_64

对于这些程序包，我们可以使用yum来安装，用如下命令安装即可，

yum -y install device-mapper device-mapper-multipath。

（2）启动multipath，并修改为自启动。

/etc/init.d/multipathd start，执行这个命令，启动multipath。

chkconfig --level 35 multipathd on，执行这个命令修为自启动。

（3）配置/etc/multipath.conf文件。

该文件的模板，我们可以在/usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf这里找到，然后把这个文件复制到/etc目录下，可以执行如下命令，

cp /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf /etc/multipath.conf。然后编辑/etc/mulitpath.conf文件，进行如下的修改，

# This is a basic configuration file with some examples, for device mapper

# multipath.

# For a complete list of the default configuration values, see

# /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.defaults

# For a list of configuration options with descriptions, see

# /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.annotated

# REMEMBER: After updating multipath.conf, you must run

# service multipathd reload

# for the changes to take effect in multipathd

## By default, devices with vendor = "IBM" and product = "S/390.*" are

## blacklisted. To enable mulitpathing on these devies, uncomment the

## following lines.

#blacklist_exceptions {

# device {

# vendor "IBM"

# product "S/390.*"

# }

## Use user friendly names, instead of using WWIDs as names.

#defaults {

# user_friendly_names yes

## Here is an example of how to configure some standard options.

defaults {

udev_dir /dev

polling_interval 10

path_selector "round-robin 0"

path_grouping_policy multibus

getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"

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

}

## The wwid line in the following blacklist section is shown as an example

## of how to blacklist devices by wwid. The 2 devnode lines are the

## compiled in default blacklist. If you want to blacklist entire types

## of devices, such as all scsi devices, you should use a devnode line.

## However, if you want to blacklist specific devices, you should use

## a wwid line. Since there is no guarantee that a specific device will

## not change names on reboot (from /dev/sda to /dev/sdb for example)

## devnode lines are not recommended for blacklisting specific devices.

blacklist {

wwid 26353900f02796769

devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"

devnode "^hd[a-z]"

}

#multipaths {

# multipath {

# wwid 3600508b4000156d700012000000b0000

# alias yellow

# path_grouping_policy multibus

# path_checker readsector0

# path_selector "round-robin 0"

# failback manual

# rr_weight priorities

# no_path_retry 5

# }

# multipath {

# wwid 1DEC_____321816758474

# alias red

# }

#devices {

# device {

# vendor "COMPAQ "

# product "HSV110 (C)COMPAQ"

# path_grouping_policy multibus

# getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n"

# path_checker readsector0

# path_selector "round-robin 0"

# hardware_handler "0"

# failback 15

# rr_weight priorities

# no_path_retry queue

# }

# device {

# vendor "COMPAQ "

# product "MSA1000 "

# path_grouping_policy multibus

# }

其中，blacklist用来添加设备的黑名单，也就是说，设置某些设备，不让它多路径化。比如，我们可以把某些设备的wwid加入在这里。

（4）执行如下命令。

modprobe dm-multipath

multipath -F

multipath dm-multipath

multipath dm-round-robin

/etc/init.d/multipathd restart

执行完成上述命令之后，会在/etc/multipath目录下生成一个bindings这的一个文件，如下，

[root@djp01 multipath]# pwd

/etc/multipath

[root@djp01 multipath]# cat bindings

# Multipath bindings, Version : 1.0

# NOTE: this file is automatically maintained by the multipath program.

# You should not need to edit this file in normal circumstances.

# Format:

# alias wwid

mpatha 14f504e46494c45526776753764752d695267332d675a4a32

mpathb 14f504e46494c4552446f646c47592d325053352d33634f42

mpathc 14f504e46494c45524559737259462d7a4278572d6b307253

mpathd 14f504e46494c45524c693336494f2d517450512d4c6d3730

mpathe 14f504e46494c45527448484b6f432d575472632d41393944

[root@djp01 multipath]#

这里存放的是多路径的磁盘名称和对应的ID。这时，我们可以使用fdisk -l这个命令查看到这些设备，比如/dev/mapper/mpatha。

（5）再次修改/etc/multipath.conf文件，对应ID对应设备的别名。

由于上述的设备名称的可读性不是很好，所以我们要加入方便我们快速读的名称。修改/etc/multipath.conf文件，内容如下：

[root@djp01 multipath]# cat /etc/multipath.conf