Sundaramurthy Blog

January 22, 2010

Multipath/EMC power path Setup (Redhat Linux)

Filed under: Linux — sundar5 @ 12:06 am

Multipath is used between host(s) and Storage array to avoid single point of faliure
at I/O channels. It also give I/O balance between the path.
Oracle Automatic Storage Management (ASM) on NetApp storage and have a better I/O
performance, you should to build ASM disks on either iSCSI or FCP devices on
NFS filesystem.  In Linux it is called native multipath (dm-multipath).

Multipath requires two packages:

– device-mapper
– multipath-tool

Note: device-mapper package is always installed by default

Install and configure Linux multipath:

1. Download the latest package from https://rhn.redhat.com and
install it on all hosts

# rpm -Uvh device-mapper-1.02.21-1.el4

2. Check the multipath rpm installation

# rpm -qa |grep mapper
device-mapper-1.02.21-1.el4
device-mapper-multipath-debuginfo-0.4.5-27.el4_6.3.0.1
device-mapper-multipath-0.4.5-27.el4_6.3.0.1

3. Load the dm_multipath kernel module

# modprobe dm_multipath

4. edit the multipath.conf file under /etc directory.

I. Comment-out the following line from multipath.conf file.

# devnode_blacklist { devnode “*” }

II. If you want Exclude internal drives (local drives), use the bellow command

example : devnode_blacklist {
devnode “^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*”
devnode “^hd[a-z]”

III. Create a device-specific section at the end of the file for the storage system as follow:

devices {
device {
vendor “NETAPP”
product “LUN”
path_grouping_policy multibus
features “1 queue_if_no_path”
path_checker readsector0
failback immediate
}
}

5.Add the multipath service to the boot sequence

#chkconfig –add multipathd
#chkconfig –list multipathd
#chkconfig multipathd on

6. Start the multipath daemon

#/etc/init.d/multipathd start

7.  Check multipath command.

# multipath -ll

mpath1 (360060160ae888a00e8b5892f190bdd33)
[size=146 GB][features=”1 queue_if_no_path”][hwhandler=”1 emc”]
\_ round-robin 0 [prio=4][active]
\_ 5:0:2:2   sdabd 133:688  [active][ready]
\_ 6:0:2:2   sdaob 66:1200  [active][ready]
\_ 1:0:2:2   sdbh  67:176   [active][ready]
\_ 2:0:2:2   sdof  128:432  [active][ready]
\_ round-robin 0 [enabled]
\_ 5:0:3:2   sdacf 135:624  [active][ready]
\_ 6:0:3:2   sdapd 68:1136  [active][ready]
\_ 1:0:3:2   sdcj  69:112   [active][ready]
\_ 2:0:3:2   sdph  130:368  [active][ready]

mpath2 (3600601603fb99c00fe8278261b0bdd33)
[size=146 GB][features=”1 queue_if_no_path”][hwhandler=”1 emc”]
\_ round-robin 0 [prio=4][active]
\_ 5:0:5:13  sdaeu 67:928   [active][ready]
\_ 6:0:5:13  sdars 128:1184 [active][ready]
\_ 1:0:5:13  sdey  129:160  [active][ready]
\_ 2:0:5:13  sdrw  134:416  [active][ready]
\_ round-robin 0 [enabled]
\_ 5:0:4:13  sdads 65:992   [active][ready]

II. Disable multipath

1. Take a copy of /etc/multipath.conf

cp /etc/multipath.conf /etc/multipath.conf_20080710

2. root user: Edit /etc/multipath.conf file and commentout all the entries in the file as root user

3. root user: Make sure the below entry in the multipath.conf file

blocklist {
devnode “*”
}

4. Take out the output of below command

sudo multipath -ll > /tmp/mpio_nodename.lst

5. disbale multipath process by using following command as root user.

# dmsetup ls   — displays all the device mapper
# /etc/init.d/multipathd stop
# /sbin/chkconfig multipathd off
# /sbin/dmsetup remove_all
# /sbin/rpm -e `rpm -qa | grep multipath`

6. Reboot the server

III. power path Installation

1. Download the PowerPath archive from

http://Powerlink.EMC.com > Support > Software Downloads and Licensing > Downloads D-R > PowerPath for Linux

2. # tar -xzf EMCpower.LINUX-5.3.1.00.00-111.tar.gz

3. # rpm -I EMCpower.LINUX-5.3.1.00.00-111.rhel5.x86_64.rpm

4. # rpm -ivh EMCpower.LINUX-5.3.1.00.00-111.rhel5.x86_64.rpm

Preparing…                ########################################### [100%]
1:EMCpower.LINUX         ########################################### [100%]
All trademarks used herein are the property of their respective owners.
NOTE:License registration is not required to manage the CLARiiON AX series array.

5. Apply license on EMC Powerpath (Registration)

# emcpreg -install

===========   EMC PowerPath Registration ===========
Do you have a new registration key or keys to enter?[n] y

Enter the registration keys(s) for your product(s),
one per line, pressing Enter after each key.
After typing all keys, press Enter again.
Key (Enter if done): “enter emc-powerpath-license-key

–> Enter the 24-character alphanumeric sequence found on the
License Key Card delivered with the PowerPath media kit

1 key(s) successfully added.
Key successfully installed.

1 key(s) successfully registered.

6.       /etc/init.d/PowerPath start

Starting PowerPath: done

7.      # rpm -qa |grep EMC

EMCpower.LINUX-5.3.1.00.00-111

8. #reboot
9. # Confirm devices /sbin/powermt display dev=all


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