Requirements:
1) RHEL 6.x (most apply to RHEL 5.x too, RHEL 5.x use mkinitrd instead of Dracut and the /etc/multipath.conf is slightly different refer to Red Hat KB in reference section)
2) EMC storage was setup with Active/Active (ALUA)
3) Boot LUN was presented with single path for initial install
Procedures:
1. Server boots up after initial install
2. Login to server as root to enable multipath
[root@server1]#mpathconf --enable –-with_multipathd y
3. Edit /etc/multipath.conf and make sure it only contains following valid parameters
[root@server1]#multipath –v3
It should be /dev/mapper/mpatha
5. Create initramfs with multipath module
[root@server1]#dracut --force -–add multipath
6. Make sure multipath.conf is included in initrd image
8. Reboot the server.
9. Verify multipath, check hwhandler='1 alua' and member disk sda for mpatha
NOTE: any change to /etc/multipath.conf requires re-create initramfs ( dracut --force -–add multipath) and a reboot, because the boot LUN is on SAN, if boot LUN is local disk, change to /etc/multipath.conf only requires multipathd restart
1) RHEL 6.x (most apply to RHEL 5.x too, RHEL 5.x use mkinitrd instead of Dracut and the /etc/multipath.conf is slightly different refer to Red Hat KB in reference section)
2) EMC storage was setup with Active/Active (ALUA)
3) Boot LUN was presented with single path for initial install
Procedures:
1. Server boots up after initial install
2. Login to server as root to enable multipath
[root@server1]#mpathconf --enable –-with_multipathd y
3. Edit /etc/multipath.conf and make sure it only contains following valid parameters
blacklist {4.Find out the logical path the root disk is mapped
}
defaults {
user_friendly_names yes
}
devices {
device {
vendor "DGC"
product ".*"
product_blacklist "LUNZ"
hardware_handler "1 alua"
path_checker directio
prio alua
}
}
[root@server1]#multipath –v3
It should be /dev/mapper/mpatha
5. Create initramfs with multipath module
[root@server1]#dracut --force -–add multipath
6. Make sure multipath.conf is included in initrd image
[root@server1]#lsinitrd /boot/initramfs-*.x86_64.img | grep multipath.conf7. Modify the /boot/grub/device.map and change
-rw-r--r-- 1 root root 2525 Feb 27 13:31 etc/multipath.conf
(hd0) /dev/sda toThis is assuming the boot disk is on /dev/mapper/mpatha as verified in step 2 above.
(hd0) /dev/mapper/mpatha
8. Reboot the server.
9. Verify multipath, check hwhandler='1 alua' and member disk sda for mpatha
[root@server1]#multipath –ll13. Partition other LUNS using fdisk command as normal, but use logical path /dev/mapper/mpathb etc (partition will be created as /dev/mapper/mpathbp1 instead of /dev/mapper/mpathb1
mpatha (3600601609973310067eb1e1ed69ae311) dm-0 DGC,VRAID
size=150G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
`-+- policy='round-robin 0' prio=10 status=enabled
|- 1:0:0:0 sda 8:0 active ready running
10. Ask storage administrator to enable other paths for boot LUN.
11. Reboot server again after multipath is aenabled in storage too
12. Login server to verify all paths, check hwhandler='1 alua' prio>0
if hwhandler='1 emc' or prio=0 means PNR mode
[root@server1]#multipath -ll
mpatha (3600601609973310067eb1e1ed69ae311) dm-0 DGC,VRAID
size=150G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=130 status=active
| |- 1:0:1:0 sdd 8:48 active ready running
| `- 2:0:1:0 sdj 8:144 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
|- 1:0:0:0 sda 8:0 active ready running
`- 2:0:0:0 sdg 8:96 active ready running
mpathb (360060160997331009fd6e124d69ae311) dm-1 DGC,VRAID
size=800G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=130 status=active
| |- 1:0:0:1 sdb 8:16 active ready running
| `- 2:0:0:1 sdh 8:112 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
|- 1:0:1:1 sde 8:64 active ready running
`- 2:0:1:1 sdk 8:160 active ready running
NOTE: any change to /etc/multipath.conf requires re-create initramfs ( dracut --force -–add multipath) and a reboot, because the boot LUN is on SAN, if boot LUN is local disk, change to /etc/multipath.conf only requires multipathd restart