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8) In order to allow multipath I/O access from the SLES server, the multipath software
on the server needs to be configured. Check the installation status of the multipath
package and install (if needed):
# rpm –q device-mapper
device-mapper-1.02.27-8.17.20.
9) SLES does not automatically create /etc/multipath.conf file. Perform the following
copy to create the file.
# cp /usr/share/doc/packages/multipath-tools/multipath.conf.synthetic
/etc/multipath.conf
10) Setup the server’s multipath software for the PS Series array by editing the
multipath configuration file and starting the multipath daemon. The multipath
configuration file (/etc/multipath.conf) contains these sections: blacklist; defaults;
multipaths and devices. Devices included in the blacklist section are excluded as
multipath candidates. The default multipath configuration file blacklists all devices
with a blacklist section that looks like this:
# Blacklist all devices by default. Remove this to enable
# multipathing on the default devices.
#
blacklist {
devnode “*”
}
The server’s multipath daemon should be enabled on the PS Series array, but not
on the local SCSI disk. In order to accomplish this, the blacklist section of the
multipath configuration file needs to be modified. The test configuration had one
direct attached SCSI drive, /dev/sda. The World Wide Identifier (WWID) is a unique
and persistent name for a SCSI device. The WWID is used to specify this particular
device in the multipath configuration file. The WWID for /dev/sda on the test
configuration was acquired using this command:
# ls -l /dev/disk/by-id
total 0
lrwxrwxrwx 1 root root 9 Jul 13 12:43 scsi-
3600508e0000000009d26af2c9525700d -> ../../sda
lrwxrwxrwx 1 root root 10 Jul 13 12:43 scsi-
3600508e0000000009d26af2c9525700d-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 Jul 13 12:43 scsi-
3600508e0000000009d26af2c9525700d-part2 -> ../../sda2
lrwxrwxrwx 1 root root 9 Jul 13 12:44 scsi-
36090a0286066ee8aa9c124021ee11685 -> ../../sdb
Using this information, the blacklist section of the configuration file was changed to
this, excluding the local SCSI disk from multipathing:
blacklist {
wwid 3600508e0000000009d26af2c9525700d