Installation guide

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Configuring Storage Access with Device Mapper Multipath

Red Hat Enterprise Linux supports large variety of storage devices with native Linux multipathing. As an exam-

ple, we will show the configuration for EMC CLARiiON and SYMMETRIX storage arrays.

The following steps detail the procedure for configuring multipath on a Red Hat Enterprise Linux 5 host.

1. If the device-mapper-multipath package is not installed as part of the default operating system installa-

tion install the package:

# yum install device-mapper-multipath

2. Load the dm_multipath kernel module if it is not already loaded.

# modprobe dm_multipath

3. Replace the default /etc/multipath.conf with the following multipath.conf file.

defaults {

path_grouping_policy failover

user_friendly_names yes

}

#multipaths {

# multipath {

# wwid 3600508b4000156d700012000000b0000

# alias asm1

# }

devices {

## Device attributes for EMC CLARiiON

device {

vendor "DGC"

product "*"

product_blacklist “(LUNZ|LUN_Z)”

path_grouping_policy group_by_prio

getuid_callout "/sbin/scsi_id -g -u -s /block/%n"

prio_callout "/sbin/mpath_prio_emc /dev/%n"

path_checker emc_clariion

path_selector "round-robin 0"

features "1 queue_if_no_path"

no_path_retry 300

hardware_handler "1 emc"

failback immediate

}

## Device attributes for EMC Symmetrix

device {

vendor “EMC”

product “SYMMETRIX”

path_grouping_policy multibus

getuid_callout “/sbin/scsi_id -g -u -ppre-spc3-83 -s /block/%n”

path_checker readsector0

features “1 queue_if_no_path”

no_path_retry 60

hardware_handler “0”

rr_weight uniform

rr_min_io 10

}