Applies To:

Oracle Database         Oracle 12cR1 12.1.0.1.0 Enterprise Edition

Operating System(s)   Red Hat Enterprise Linux with kernel 2.6.32-431.el6.x86_64

 

Storage                    EqualLogic Storage Array PS6110

Problem:

How to configure multipath for EqualLogic Storage Array PS6110?

Solution:

Device mapper multipath utility is used to achieve consistent naming of shared volumes across all nodes in a RAC set up.

The four components of a multipath configuration file are:

  • blacklist
  • blacklist exceptions
  • defaults &
  • multipaths

The wiki article How to configure device-mapper-multipath provides the steps involved in configuring the /etc/multipath.conf file. However for the purpose of deploying the Oracle RAC12cR1 on RHEL 6.5, with EqualLogic PS6110 as the storage, the defaults section of the multipath configuration file needs to have the values given below: 

defaults {

       udev_dir                   /dev

       polling_interval       10

       path_selector              "round-robin 0"

       path_grouping_policy   multibus

       getuid_callout            "/lib/udev/scsi_id --whitelisted --device=/dev/%n"

       prio                           alua

       path_checker              tur

       rr_min_io                    100

       max_fds                      8192

       rr_weight                    priorities

       failback                    immediate

       no_path_retry              fail

       user_friendly_names     yes

}

Of particular interest is the path checker attribute which specifies the default method used to determine the state of the paths. If it is set to read sector0 it reads the first sector of the device. When set to a value of "tur" Test Unit Ready, it issues a TUR to the device. For Equallogic PS 6110 the path checker attribute needs to be set to "tur".