How to configure device-mapper-multipath

How to configure device-mapper-multipath

Applies to:

Enterprise Linux 5.x


How do I configure device-mapper-multipath?


1. Verify that your device-mapper and multipath driver are at least the version shown below or higher by running the command: rpm -qa | grep device-mapper


2. Identify your local disks i.e. /dev/sda. Once your local disk is determined run the following command to obtain its scsi_id: scsi_id –gus /block/sda


3. Open the /etc/multipath.conf file and locate and comment out the section below:

#blacklist {
# devnode "*"

4. Once the scsi_id of your local disk has been retrieved, you must blacklist this scsi_id from being used as a multipath device. Within /etc/multipath.conf file and locate, uncomment, and modify the section below:

blacklist {
wwid <enter your local disk scsi_id here>
devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
devnode "^hd[a-z]"

5. Uncomment your defaults section within your /etc/multipath.conf

defaults {
udev_dir /dev
polling_interval 10
selector "round-robin 0"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
prio_callout /bin/true
path_checker readsector0
rr_min_io 100
max_fds 8192
rr_weight priorities
failback immediate
no_path_retry fail
user_friendly_names yes

6. Locate the multipaths section within your /etc/multipath.conf file. In this section you will provide the scsi_id of each iSCSI volume and provide an alias in order to keep a consistent naming convention across all of your OVM Server nodes. An example is shown below:

multipaths {
multipath {
wwid <scsi_id of volume1>
alias alias_of_volume1
multipath {
wwid <scsi_id of volume2>
alias alias_of_volume2
NOTE: Additional multipath subsections can be added to meet the number of volumes you need.

7. Restart your multipath daemon service using the following command:

service multipathd restart

8. Verify that your multipath volumes alias are displayed properly by running the following command: multipath –ll

Alias_of_volume1 (scsi_id of volume1) dm-2 EQLOGIC,100E-00
\_ round-robin 0 [prio=0][active]
\_ 6:0:0:0 sdaj 66:48 [active][ready]
\_ 4:0:0:0 sdag 66:0 [active][ready]
\_ 3:0:0:0 sdd 8:48 [active][ready]
\_ 5:0:0:0 sdn 8:208 [active][ready]

9. Make sure the iSCSI service starts upon boot using the command:

chkconfig multipathd on

  1. This article is an adaptation of an excerpt from Dell Engineer Roger Lopez's whitepaper on "Best Practices and Performance Characteristics of Running Oracle® RAC 11g with Dell EqualLogic™ on Oracle VM" and can be found here.

Article ID: SLN310271

Last Date Modified: 08/17/2018 07:27 AM

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