linux下磁盘多路径multipath使用方法

[root@liujing mapper]# multipath -ll

mpatha (360a9800064665072443469563477396c) dm-0 NETAPP,LUN ----创建了一个lun

size=3.5G features='0' hwhandler='0' wp=rw

`-+- policy='round-robin 0' prio=4 status=active

|- 1:0:0:0 sdb 8:16 active ready running ----多路径下的两个盘符sdb和sde.

`- 2:0:0:0 sde 8:64 active ready running

目录/dev/mapper/ 下多了两个文件夹mpatha 和mpathap1。

[root@liujing mapper]# cd /dev/mapper/

[root@liujing mapper]# ls

control mpatha mpathap1

同时fdisk –l的命令下也多了两个设备标识：

没有配置多路径时：

[root@liujing~]# fdisk -l

Disk /dev/sda: 146.8 GB, 146815733760 bytes

255 heads, 63 sectors/track, 17849 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x000a6cdd

Device Boot Start End Blocks Id System

/dev/sda1 * 1 26 204800 83 Linux

Partition 1 does not end on cylinder boundary.

/dev/sda2 26 287 2097152 82 Linux swap / Solaris

Partition 2 does not end on cylinder boundary.

/dev/sda3 287 17850 141071360 83 Linux

Disk /dev/sdb: 3774 MB, 3774873600 bytes

117 heads, 62 sectors/track, 1016 cylinders

Units = cylinders of 7254 * 512 = 3714048 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Disk identifier: 0xac956c3a

Device Boot Start End Blocks Id System

/dev/sdb1 1 1016 3685001 83 Linux

Partition 1 does not start on physical sector boundary.

Disk /dev/sde: 3774 MB, 3774873600 bytes

117 heads, 62 sectors/track, 1016 cylinders

Units = cylinders of 7254 * 512 = 3714048 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Disk identifier: 0xac956c3a

Device Boot Start End Blocks Id System

/dev/sde1 1 1016 3685001 83 Linux

Partition 1 does not start on physical sector boundary.

两个CAN网卡获取到同一盘符：

/dev/sde和/dev/sdb.

配置后多了/dev/mapper/mpatha和/dev/mapper/mpathap1：

[root@localhost mapper]# fdisk -l

Disk /dev/sda: 146.8 GB, 146815733760 bytes

255 heads, 63 sectors/track, 17849 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x000a6cdd

Device Boot Start End Blocks Id System

/dev/sda1 * 1 26 204800 83 Linux

Partition 1 does not end on cylinder boundary.

/dev/sda2 26 287 2097152 82 Linux swap / Solaris

Partition 2 does not end on cylinder boundary.

/dev/sda3 287 17850 141071360 83 Linux

Disk /dev/sdb: 3774 MB, 3774873600 bytes

117 heads, 62 sectors/track, 1016 cylinders

Units = cylinders of 7254 * 512 = 3714048 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Disk identifier: 0xac956c3a

Device Boot Start End Blocks Id System

/dev/sdb1 1 1016 3685001 83 Linux

Partition 1 does not start on physical sector boundary.

Disk /dev/sde: 3774 MB, 3774873600 bytes

117 heads, 62 sectors/track, 1016 cylinders

Units = cylinders of 7254 * 512 = 3714048 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Disk identifier: 0xac956c3a

Device Boot Start End Blocks Id System

/dev/sde1 1 1016 3685001 83 Linux

Partition 1 does not start on physical sector boundary.

Disk /dev/mapper/mpatha: 3774 MB, 3774873600 bytes

117 heads, 62 sectors/track, 1016 cylinders

Units = cylinders of 7254 * 512 = 3714048 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Disk identifier: 0xac956c3a

Device Boot Start End Blocks Id System

/dev/mapper/mpathap1 1 1016 3685001 83 Linux

Partition 1 does not start on physical sector boundary.

Disk /dev/mapper/mpathap1: 3773 MB, 3773441024 bytes

255 heads, 63 sectors/track, 458 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 4096 bytes / 65536 bytes

Alignment offset: 1024 bytes

Disk identifier: 0x00000000

Disk /dev/mapper/mpathap1 doesn't contain a valid partition table

multipath -F #删除现有路径 两个新的路径就会被删除

multipath -v2 #格式化路径 格式化后又出现

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3. multipath磁盘的基本操作

要对多路径软件生成的磁盘进行操作直接操作/dev/mapper/目录下的磁盘就行.

在对多路径软件生成的磁盘进行分区之前最好运行一下pvcreate命令:

pvcreate /dev/mapper/mpatha

fdisk /dev/mapper/mpatha 分区时用这个目录/dev/mapper/mpatha

用fdisk对多路径软件生成的磁盘进行分区保存时会有一个报错,此报错不用理会.

ls -l /dev/mapper/

[root@liujing mnt]# ls -l /dev/mapper/

total 0

crw-rw----. 1 root root 10, 58 Mar 10 19:10 control

lrwxrwxrwx. 1 root root 7 Mar 10 20:28 mpatha -> ../dm-0

lrwxrwxrwx. 1 root root 7 Mar 10 20:33 mpathap1 -> ../dm-1

的mpathap1就是我们对multipath磁盘进行的分区

mkfs.ext4 /dev/mapper/mpathap1 #对mpath1p1分区格式化成ext4文件系统

mount /dev/mapper/mpathap1 /mnt/ #挂载mpathap1分区

格式化和挂载时用/dev/mapper/mpathap1

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4. 分区磁盘：

上面有提到分区时用目录/dev/mapper/mpatha

[root@liujing~]# fdisk /dev/mapper/mpatha

Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel

Building a new DOS disklabel with disk identifier 0xac956c3a.

Changes will remain in memory only, until you decide to write them.

After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to

switch off the mode (command 'c') and change display units to

sectors (command 'u').

Command (m for help): n------------------------新建分区

Command action

e extended

p primary partition (1-4)

p-----------------------------主分区

Partition number (1-4): 1

First cylinder (1-1016, default 1):

Using default value 1

Last cylinder, +cylinders or +size{K,M,G} (1-1016, default 1016):

Using default value 1016

Command (m for help): w ---------------------写入列表相当于保存

The partition table has been altered!

Calling ioctl() to re-read partition table.

Syncing disks.

注：如果同一台设备的两个node挂同样的盘符，另一个盘符还需要再次写入w就行。不需要n了。

5. 格式化：

[root@liujing ~]# mkfs.ext4 /dev/mapper/mpathap1

mke2fs 1.41.12 (17-May-2010)

/dev/sdd1 alignment is offset by 1024 bytes.

This may result in very poor performance, (re)-partitioning suggested.

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

Stride=1 blocks, Stripe width=16 blocks

230608 inodes, 921250 blocks

46062 blocks (5.00%) reserved for the super user

First data block=0

Maximum filesystem blocks=943718400

29 block groups

32768 blocks per group, 32768 fragments per group

7952 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912, 819200, 884736

Writing inode tables: done

Creating journal (16384 blocks): done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 33 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.

Using Linux Iotop to check disk IO usage Per process

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挂载 /dev/mapper/mpathap1 到 /mnt

[root@liujing ~]# mount /dev/mapper/mpathap1 /mnt

三、multipath的高级配置之前的配置都是用multipath的默认配置来完成multipath，比如映射设备的名称，multipath负载均衡的方法都是默认设置。那有没有按照我们自己定义的方法来配置multipath呢，答案是OK。

1、multipath.conf文件的配置

接下来的工作就是要编辑/etc/multipath.conf的配置文件

multipath.conf主要包括blacklist、multipaths、devices三部份的配置

blacklist配置

blacklist {

devnode "^sda"

}

Multipaths部分配置multipaths和devices两部份的配置。

multipaths {

multipath {

wwid ** #此值multipath -v3可以看到

alias iscsi-dm0 #映射后的别名,可以随便取

path_grouping_policy multibus #路径组策略

path_checker tur #决定路径状态的方法

path_selector "round-robin 0" #选择那条路径进行下一个IO操作的方法

}

}

Devices部分配置

devices {

device {

vendor "iSCSI-Enterprise" #厂商名称

product "Virtual disk" #产品型号

path_grouping_policy multibus #默认的路径组策略

getuid_callout "/sbin/scsi_id -g -u -s /block/%n" #获得唯一设备号使用的默认程序

prio_callout "/sbin/acs_prio_alua %d" #获取有限级数值使用的默认程序

path_checker readsector0 #决定路径状态的方法

path_selector "round-robin 0" #选择那条路径进行下一个IO操作的方法

failback immediate #故障恢复的模式

no_path_retry queue #在disable queue之前系统尝试使用失效路径的次数的数值

rr_min_io 100 #在当前的用户组中，在切换到另外一条路径之前的IO请求的数目

}

}

在我本地的一个完整的高级配置如下：

[root@liujing ~]# vi /etc/multipath.conf

blacklist {

devnode "^sda"

}

multipaths {

multipath {

wwid 360a98000646650724434697454546156

alias mpathb_fcoe

path_grouping_policy multibus

path_checker "directio"

prio "random"

path_selector "round-robin 0"

}

}

devices {

device {

vendor "NETAPP"

product "LUN"

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

path_checker "directio" path_selector "round-robin 0"

failback immediate

no_path_retry fail

}

}

其中 wwid，vendor，product， getuid_callout这些参数可以通过：multipath -v3命令来获取。如果在/etc/multipath.conf中有设定各wwid 别名,别名会覆盖此设定。

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四、负载均衡测试：

可以使用dd命令来对设备进行读写操作，并同时通过iostat来查看I／0状态，流量从哪个路径出去：

DD命令：dd if=/dev/zero of=/mnt/1Gfile bs=8k count=131072 在上面我们已经把磁盘挂载在/MNT文件夹下所以我们在读写磁盘时直接对/mnt文件夹直接读写就可以了。

如果想对磁盘重复读写可以用如下语句：

[root@liujing ~]# for ((i=1;i&1|grep MB;done; ---重复读写5次这个值可以根据自己测试需求修改。

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另一个控制台输入iostat 2 10查看IO读写状态：

可以看到sdc和sdd是两个多路径的盘符，流量均匀的负载在两条路径中unix路径简化，负载均衡很成功。

五、路径冗余备份测试

将其中一条路径的端口down掉，所有流量会直接切换到另一个路径中。

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