Table of Contents
RHEL and CentOS need the device-mapper-multipath package.
yum install device-mapper-multipath
This will create a sample multipath.conf in /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.
There is no /etc/multipath.conf until you initialize it with mpathconf.
[root@server2 ~]# mpathconf --enable --with_multipathd y Starting multipathd daemon: [ OK ] [root@server2 ~]# wc -l /etc/multipath.conf 99 /etc/multipath.conf
You can now choose to either edit /etc/multipath.conf or use mpathconf to change this file for you.
[root@server2 ~]# grep user_friendly_names /etc/multipath.conf user_friendly_names yes # user_friendly_names yes [root@server2 ~]# mpathconf --enable --user_friendly_names n [root@server2 ~]# grep user_friendly_names /etc/multipath.conf user_friendly_names no # user_friendly_names yes [root@server2 ~]# mpathconf --enable --user_friendly_names y [root@server2 ~]# grep user_friendly_names /etc/multipath.conf user_friendly_names yes # user_friendly_names yes
This example uses three networks, make sure the iSCSI Target is connected to all three networks.
[root@server1 tgt]# ifconfig | grep -B1 192.168
eth1 Link encap:Ethernet HWaddr 08:00:27:4E:AB:8E
inet addr:192.168.1.98 Bcast:192.168.1.255 Mask:255.255.255.0
--
eth2 Link encap:Ethernet HWaddr 08:00:27:3F:A9:D1
inet addr:192.168.2.98 Bcast:192.168.2.255 Mask:255.255.255.0
--
eth3 Link encap:Ethernet HWaddr 08:00:27:94:52:26
inet addr:192.168.3.98 Bcast:192.168.3.255 Mask:255.255.255.0The same must be true for the multipath Initiator:
[root@server2 ~]# ifconfig | grep -B1 192.168
eth1 Link encap:Ethernet HWaddr 08:00:27:A1:43:41
inet addr:192.168.1.99 Bcast:192.168.1.255 Mask:255.255.255.0
--
eth2 Link encap:Ethernet HWaddr 08:00:27:12:A8:70
inet addr:192.168.2.99 Bcast:192.168.2.255 Mask:255.255.255.0
--
eth3 Link encap:Ethernet HWaddr 08:00:27:6E:99:9B
inet addr:192.168.3.99 Bcast:192.168.3.255 Mask:255.255.255.0Test the triple discovery in three networks (screenshot newer than above).
[root@centos7 ~]# iscsiadm -m discovery -t st -p 192.168.1.150 192.168.1.150:3260,1 iqn.2015-04.be.linux:target1 [root@centos7 ~]# iscsiadm -m discovery -t st -p 192.168.2.150 192.168.2.150:3260,1 iqn.2015-04.be.linux:target1 [root@centos7 ~]# iscsiadm -m discovery -t st -p 192.168.3.150 192.168.3.150:3260,1 iqn.2015-04.be.linux:target1
Time to start (or restart) both the multipathd and iscsi services:
[root@server2 ~]# service multipathd restart Stopping multipathd daemon: [ OK ] Starting multipathd daemon: [ OK ] [root@server2 ~]# service iscsi restart Stopping iscsi: [ OK ] Starting iscsi: [ OK ]
This shows fdisk output when leaving the default friendly_names option to yes. The bottom three are the multipath devices to use.
[root@server2 ~]# fdisk -l | grep Disk
Disk /dev/sda: 42.9 GB, 42949672960 bytes
Disk identifier: 0x0004f229
Disk /dev/sdb: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdc: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdd: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sde: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdf: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdg: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_root: 41.4 GB, 41448112128 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_swap: 973 MB, 973078528 bytes
Disk identifier: 0x00000000
Disk /dev/sdh: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdi: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdj: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdl: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdn: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdk: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdm: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdp: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdo: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/mpathh: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/mpathi: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/mpathj: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
[root@server2 ~]#You can list the multipath connections and devices with multipath -ll.
[root@server2 ~]# multipath -ll
mpathj (1IET 00010001) dm-4 Reddy,VBOX HARDDISK
size=1.0G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 13:0:0:1 sdh 8:112 active ready running
|-+- policy='round-robin 0' prio=1 status=enabled
| `- 12:0:0:1 sdi 8:128 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
`- 14:0:0:1 sdm 8:192 active ready running
mpathi (1IET 00010003) dm-3 Reddy,VBOX HARDDISK
size=1.0G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 13:0:0:3 sdk 8:160 active ready running
|-+- policy='round-robin 0' prio=1 status=enabled
| `- 12:0:0:3 sdn 8:208 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
`- 14:0:0:3 sdp 8:240 active ready running
mpathh (1IET 00010002) dm-2 Reddy,VBOX HARDDISK
size=1.0G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 12:0:0:2 sdl 8:176 active ready running
|-+- policy='round-robin 0' prio=1 status=enabled
| `- 13:0:0:2 sdj 8:144 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
`- 14:0:0:2 sdo 8:224 active ready running
[root@server2 ~]#The IET (iSCSI Enterprise Target) ID should match the ones you see on the Target server.
[root@server1 ~]# tgt-admin -s | grep -e LUN -e IET -e dev
LUN information:
LUN: 0
SCSI ID: IET 00010000
LUN: 1
SCSI ID: IET 00010001
Backing store path: /dev/sdb
LUN: 2
SCSI ID: IET 00010002
Backing store path: /dev/sdc
LUN: 3
SCSI ID: IET 00010003
Backing store path: /dev/sddThe rest is standard mkfs, mkdir, mount:
[root@server2 ~]# mkfs.ext4 /dev/mapper/mpathi mke2fs 1.41.12 (17-May-2010) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 65536 inodes, 262144 blocks 13107 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=268435456 8 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376 Writing inode tables: done Creating journal (8192 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 38 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. [root@server2 ~]# mkdir /srv/multipath [root@server2 ~]# mount /dev/mapper/mpathi /srv/multipath/ [root@server2 ~]# df -h /srv/multipath/ Filesystem Size Used Avail Use% Mounted on /dev/mapper/mpathi 1008M 34M 924M 4% /srv/multipath
1. Find a partner and decide who will be iSCSI Target and who will be iSCSI Initiator and Multipather. Set up Multipath as we did in the theory.
2. Uncomment the big 'defaults' section in /etc/multipath.conf and disable friendly names. Verify that multipath can work. You may need to check the manual for /lib/dev/scsi_id and for multipath.conf.
1. Find a partner and decide who will be iSCSI Target and who will be iSCSI Initiator and Multipather. Set up Multipath as we did in the theory.
Look in the theory...
2. Uncomment the big 'defaults' section in /etc/multipath.conf and disable friendly names. Verify that multipath can work. You may need to check the manual for /lib/dev/scsi_id and for multipath.conf.
vi multipath.conf
remove # for the big defaults section
add # for the very small one with friendly_names active
add the --replace-whitespace option to scsi_id.
defaults {
udev_dir /dev
polling_interval 10
path_selector "round-robin 0"
path_grouping_policy multibus
getuid_callout "/lib/udev/scsi_id --whitelisted --replace\
-whitespace --device=/dev/%n"
prio const
path_checker readsector0
rr_min_io 100
max_fds 8192
rr_weight priorities
failback immediate
no_path_retry fail
user_friendly_names no
}The names now (after service restart) look like:
root@server2 etc]# multipath -ll 1IET_00010001 dm-8 Reddy,VBOX HARDDISK size=1.0G features='0' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=active |- 17:0:0:1 sdh 8:112 active ready running |- 16:0:0:1 sdi 8:128 active ready running `- 15:0:0:1 sdn 8:208 active ready running 1IET_00010003 dm-10 Reddy,VBOX HARDDISK size=1.0G features='0' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=active |- 17:0:0:3 sdl 8:176 active ready running |- 16:0:0:3 sdm 8:192 active ready running `- 15:0:0:3 sdp 8:240 active ready running 1IET_00010002 dm-9 Reddy,VBOX HARDDISK size=1.0G features='0' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=active |- 17:0:0:2 sdj 8:144 active ready running |- 16:0:0:2 sdk 8:160 active ready running `- 15:0:0:2 sdo 8:224 active ready running
Did you blacklist your own devices ?
vi multipath.conf
--> search for blacklist:
add
devnode "^sd[a-g]"