Linux平臺的多路徑軟件multipath的使用案例
在Linux和AIX平臺都有一部分存儲產品使用操作系統自帶的多路徑軟件，包括最常見的HP和IBM的部分存儲產品，在Linux自帶的多路徑軟件叫做multipath，這篇文章以IBM N系列存儲在Linux平臺的使用為例，討論Linux平臺multipath的使用。
1.確保安裝以下的包：
device-mapper
device-mapper-multipath
2.編輯配置文件/etc/multipath.conf
[root@rac01 ~]# vi /etc/multipath.conf
defaults
{
user_friendly_names yes
max_fds max
queue_without_daemon no
flush_on_last_del yes
}
## Blacklist non-SAN devices
#sample：
#devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
#devnode "^hd[a-z]"
#devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]"
blacklist
{
wwid 3600605b002b6b890163d47661e8d4fbe
}
# FCP configuration, for a NetApp FAS3xxx / IBM Nxx00
# Vendor is "NETAPP ", spaces are important
# Product is "LUN", though "*" will do
devices
{
device
{
vendor "NETAPP"
product "LUN"
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout "/sbin/mpath_prio_ontap /dev/%n"
features "1 queue_if_no_path"
hardware_handler "0"
path_grouping_policy group_by_prio
failback immediate
rr_weight uniform
rr_min_io 128
path_checker directio
}
}
#下面的注釋配置不是必須的，配置之后可以固定系統設備的名稱，這在服務器重啟設備文件對應的磁盤設備發生變化的情況下使用。
#multipaths
#{
# multipath {
# wwid 360a9800065344e6f465a6d5773745558
# alias mocr1
# }
# multipath {
# wwid 360a9800065344e6e536f6d586d306630
# alias mocr2
# }
#}
3.啟動multipathd服務，及設置其自動啟動。
執行以下的命令：
#service multipathd restart
#chkconfig --level 345 multipathd on
#chkconfig --list | grep multipathd
4.檢查multipath聚合后的設備名，以及設備對應的鏈路情況。
[root@rac2 ~]# multipath -ll
mpath3 (360a9800065344e6f465a6d5773747545) dm-3 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:5 sdf 8:80 active ready running
`- 2:0:0:5 sdp 8:240 active ready running
mpath2 (360a9800065344e6f465a6d5773746878) dm-1 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:3 sdd 8:48 active ready running
`- 2:0:0:3 sdn 8:208 active ready running
mpath0 (360a9800065344e6f465a6d5773745558) dm-0 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:1 sdb 8:16 active ready running
`- 2:0:0:1 sdl 8:176 active ready running
mpath9 (360a9800065344e6e536f6d586d33666e) dm-9 NETAPP,LUN
size=3.9T features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:10 sdk 8:160 active ready running
`- 2:0:0:10 sdu 65:64 active ready running
mpath8 (360a9800065344e6e536f6d586d32766b) dm-7 NETAPP,LUN
size=150G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:8 sdi 8:128 active ready running
`- 2:0:0:8 sds 65:32 active ready running
mpath7 (360a9800065344e6e536f6d586d313851) dm-6 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:6 sdg 8:96 active ready running
`- 2:0:0:6 sdq 65:0 active ready running
mpath7 (360a9800065344e6e536f6d586d307464) dm-4 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:4 sde 8:64 active ready running
`- 2:0:0:4 sdo 8:224 active ready running
mpath6 (360a9800065344e6e536f6d586d306630) dm-2 NETAPP,LUN
size=2.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:2 sdc 8:32 active ready running
`- 2:0:0:2 sdm 8:192 active ready running
mpath5 (360a9800065344e6f465a6d577376304f) dm-8 NETAPP,LUN
size=3.9T features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:9 sdj 8:144 active ready running
`- 2:0:0:9 sdt 65:48 active ready running
mpath4 (360a9800065344e6f465a6d5773766c58) dm-5 NETAPP,LUN
size=150G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
|- 1:0:0:7 sdh 8:112 active ready running
`- 2:0:0:7 sdr 65:16 active ready running
從以上的結果可以看出，每個磁盤設備對應的是兩條鏈路，根據不存的存儲以及不同的配置會有所不同。每個設備都有兩個multipath設備名，分別是mpath[x]和dm-[x]，mpath位于/dev/mpath目錄下，dm-[x]位于/dev目錄下。通常推薦使用/dev/mpath目錄下的設備名，這對于我們來說更加的方便。
5.下面我們重點關注一下fdisk -l執行的結果。
[root@rac2 ~]# fdisk -l
Disk /dev/sda: 145.9 GB, 145999527936 bytes
255 heads, 63 sectors/track, 17750 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 64 514048+ 83 Linux
/dev/sda2 65 6438 51199155 83 Linux
/dev/sda3 6439 7743 10482412+ 82 Linux swap / Solaris
/dev/sda4 7744 17750 80381227+ 5 Extended
/dev/sda5 7744 17750 80381196 83 Linux
Disk /dev/sdb: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 261 2096451 83 Linux
Disk /dev/sdd: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdd1 1 261 2096451 83 Linux
Disk /dev/sdf: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdf1 1 261 2096451 83 Linux
Disk /dev/sdc: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc1 1 261 2096451 83 Linux
Disk /dev/sde: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sde1 1 261 2096451 83 Linux
Disk /dev/sdh: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdh2 1 19581 157284351 83 Linux
Disk /dev/sdg: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdg1 1 261 2096451 83 Linux
Disk /dev/sdi: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdi1 1 19581 157284351 83 Linux
WARNING: GPT (GUID Partition Table) detected on '/dev/sdj'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/sdj: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdj1 1 267350 2147483647+ ee EFI GPT
WARNING: GPT (GUID Partition Table) detected on '/dev/sdk'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/sdk: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdk1 1 267350 2147483647+ ee EFI GPT
Disk /dev/sdl: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdl1 1 261 2096451 83 Linux
Disk /dev/sdm: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdm1 1 261 2096451 83 Linux
Disk /dev/sdn: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdn1 1 261 2096451 83 Linux
Disk /dev/sdp: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdp1 1 261 2096451 83 Linux
Disk /dev/sdo: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdo1 1 261 2096451 83 Linux
Disk /dev/sdr: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdr1 1 19581 157284351 83 Linux
Disk /dev/sdq: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdq1 1 261 2096451 83 Linux
Disk /dev/sds: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sds1 1 19581 157284351 83 Linux
WARNING: GPT (GUID Partition Table) detected on '/dev/sdt'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/sdt: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdt1 1 267350 2147483647+ ee EFI GPT
WARNING: GPT (GUID Partition Table) detected on '/dev/sdu'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/sdu: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdu1 1 267350 2147483647+ ee EFI GPT
這之前的設備是/dev/sd[n]的設備名，這部分設備是沒有聚合的設備，根據上面顯示的兩條鏈路，那么相同的LUN應該對應兩個sd[n]設備，這部分不是使用的設備，可以不關注。
Disk /dev/dm-0: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-0p1 1 261 2096451 83 Linux
Disk /dev/dm-1: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-1p1 1 261 2096451 83 Linux
Disk /dev/dm-2: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-2p1 1 261 2096451 83 Linux
Disk /dev/dm-3: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-3p1 1 261 2096451 83 Linux
Disk /dev/dm-4: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-4p1 1 261 2096451 83 Linux
Disk /dev/dm-5: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-5p1 1 19581 157284351 83 Linux
Disk /dev/dm-6: 2147 MB, 2147483648 bytes
255 heads, 63 sectors/track, 261 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-6p1 1 261 2096451 83 Linux
Disk /dev/dm-7: 161.0 GB, 161061273600 bytes
255 heads, 63 sectors/track, 19581 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-7p1 1 19581 157284351 83 Linux
WARNING: GPT (GUID Partition Table) detected on '/dev/dm-8'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/dm-8: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-8p1 1 267350 2147483647+ ee EFI GPT
WARNING: GPT (GUID Partition Table) detected on '/dev/dm-9'! The util fdisk doesn't support GPT. Use GNU Parted.
WARNING: The size of this disk is 4.2 TB (4241280204800 bytes).
DOS partition table format can not be used on drives for volumes
larger than 2.2 TB (2199023255040 bytes). Use parted(1) and GUID
partition table format (GPT).
Disk /dev/dm-9: 4241.2 GB, 4241280204800 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/dm-9p1 1 267350 2147483647+ ee EFI GPT
這部分設備分別是/dev/dm-[n]以及它們的分區/dev/dm-[n]p1，這部分是安裝好multipath多路徑軟件及針對每個磁盤設備分區后產生的，但實際在/dev/目錄下不存在dm-[n]p1這部分設備文件，只需要了解即可。
Disk /dev/dm-10: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-10 doesn't contain a valid partition table
Disk /dev/dm-11: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-11 doesn't contain a valid partition table
Disk /dev/dm-12: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-12 doesn't contain a valid partition table
Disk /dev/dm-13: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-13 doesn't contain a valid partition table
Disk /dev/dm-14: 161.0 GB, 161059175424 bytes
255 heads, 63 sectors/track, 19580 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-14 doesn't contain a valid partition table
Disk /dev/dm-15: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-15 doesn't contain a valid partition table
Disk /dev/dm-16: 161.0 GB, 161059175424 bytes
255 heads, 63 sectors/track, 19580 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-16 doesn't contain a valid partition table
Disk /dev/dm-17: 4241.2 GB, 4241280170496 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-17 doesn't contain a valid partition table
Disk /dev/dm-18: 4241.2 GB, 4241280170496 bytes
255 heads, 63 sectors/track, 515639 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-18 doesn't contain a valid partition table
Disk /dev/dm-19: 2146 MB, 2146765824 bytes
255 heads, 63 sectors/track, 260 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-19 doesn't contain a valid partition table
這部分設備名是/dev/dm-[n]，這部分設備并不是multipath多路徑軟件聚合后的磁盤設備，而是做完分區的分區設備文件，再剛對前面的/dev/dm-0，dev/dm-1做完分區之后執行fdisk -l是看不到這部分設備信息的，只有重啟之后才看到這些設備信息并產生了相應的設備文件。例如，/dev/dm-10對應的是/dev/dm-0p1，/dev/dm-11對應的是/dev/dm-1p1，以此類推，這部分設備文件可以被使用，但由于這些設備文件對應multipath聚合的磁盤設備比較麻煩，所以并不推薦使用這種方式。
下面討論/dev/mpath目錄下的設備文件：
安裝完multipath軟件并配置完成之后會在/dev/mpath目錄下生成聚合后的磁盤設備文件，實際是/dev/dm-[n]的鏈接文件：
[root@rac2 mpath]# ls -al
total 0
drwxr-xr-x 2 root root 440 Sep 21 02:05 .
drwxr-xr-x 13 root root 7060 Sep 21 02:12 ..
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath0 -> ../dm-0
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath0p1 -> ../dm-19
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath2 -> ../dm-1
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath2p1 -> ../dm-10
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath3 -> ../dm-2
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath3p1 -> ../dm-17
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath4 -> ../dm-5
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath4p1 -> ../dm-12
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath5 -> ../dm-7
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath5p1 -> ../dm-14
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath6 -> ../dm-3
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath6p1 -> ../dm-18
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath7 -> ../dm-4
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath7p1 -> ../dm-11
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath7 -> ../dm-6
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath7p1 -> ../dm-13
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath8 -> ../dm-9
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath8p1 -> ../dm-16
lrwxrwxrwx 1 root root 7 Sep 21 02:05 mpath9 -> ../dm-8
lrwxrwxrwx 1 root root 8 Sep 21 02:05 mpath9p1 -> ../dm-15
從上面的輸出結果我們可以非常容易的了解到磁盤分區設備文件與磁盤設備文件之間的對應關系，所以使用/dev/mpath目錄下的文件比使用/dev/目錄下磁盤設備和磁盤分區設備文件都以dm-[n]方式表示的文件更加方便。之后我們在使用oracleasm創建ASM磁盤的時候，使用fdisk -l /dev/mpath/mpath[n]p1查看磁盤信息，直接使用/dev/mpath/mpath[n]p1作為ASM磁盤，非常的方便。
還需要注意如下幾點：
1).經過multipath多路徑軟件聚合后的設備文件(/dev/mpath/mpath[n])不會隨著服務器的重啟，對應的磁盤設備發生變化，而/dev/sd[n]對應的磁盤LUN重啟后是可能發生變化的。
2).如果單個磁盤大于2TB，那么在分區的時候不要使用fdisk工具(傳統的MBR)，應該使用parted(gpt)，使用parted工具創建gpt分區的步驟是：
#parted
PARTED> select /dev/mpath/mpath0
PARTED> mklabel gpt
PARTED> mkpart primary 0 100%
3).如果我們使用ASM作為數據庫數據文件的存儲方式，那么單個ASM磁盤的大小不能超過2TB，所以在系統分區的時候就應該做好更小的分區，例如，/dev/mpath/mpath0磁盤的大小為3.8TB，那么在分區的時候應該做如下操作：
#parted
PARTED> select /dev/mpath/mpath0
PARTED> mklabel gpt
PARTED> mkpart primary 0 50%
PARTED> mkpart primary 50% 100%
完成以上分區操作之后，重啟服務器，在/dev/mpath/目錄下就會看到mpath0p1和mpath0p2兩個設備文件，將這兩個設備文件作為ASM磁盤即可。
--end--
