IBM System Storage DS4000, Hardware Manual

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Chapter 7. Advanced maintenance, troubleshooting, and diagnostics
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7.11.5 Linux
There are two available driver options to manage a DS5000 storage subsystem in Linux:
򐂰 The RDAC/MPP driver
򐂰 The HBA failover driver
To install RDAC/MPP, a specific kernel version is required. The RDAC driver readme has
information about all the supported kernel versions. We currently recommend using RDAC as
the failover driver.
RDAC provides additional functions and utilities to obtain much better information about the
DS5000 from the operating system. Once the RDAC driver is installed, you have access to
several commands that are useful for problem determination and correction. The utilities are:
򐂰 mppUtil: This utility is used with the Linux RDAC driver to perform the various functions
provided by the driver.
򐂰 hot_add: This utility rescans your HBA to detect and configure new devices on SAN.
򐂰 mppBusRescan: This utility is equivalent to hot_add and also probes the physical bus
hardware to discover any newly attached DS5000 devices. These can either be new LUNs
on an existing system or a new storage subsystem. All the physical buses are scanned for
new devices or LUNs. Any that are found are registered with the OS and attached to the
RDAC driver. This utility should be run any time that new storage subsystem devices are
connected or new LUNs are mapped to a system.
򐂰 mppUpdate: This utility uses the mppUtil utility to discover the RDAC-assigned virtual
target IDs of the attached subsystems. It then updates the RDAC driver configuration file
(
/var/mpp/devicemapping ) so that the entries will be persistent after a reboot. The first
time that the RDAC driver sees a storage subsystem, it will arbitrarily assign a target ID for
the virtual target that represents the storage subsystem. At this point, the target ID
assignment is not persistent. It could change on a reboot. The mppUpdate utility updates
the RDAC driver configuration files so that these target ID assignments are persistent and
do not change across reboots. Once made persistent, the user does not have to worry
about the possibility of device names changing and invalidating mount points.
mppUpdate must be executed after a DS5000 is added to or removed from the system. If
a storage subsystem is added to the installation, mppBusRescan also must be run before
mppUpdate is run. mppUpdate must also be executed whenever a user changes the
RDAC configuration file
/etc/mpp.conf
to rebuild the new configuration file into the RAM
Disk image that will be used for the next reboot.
Note: Linux RDAC supports rescan of a newly mapped LUN without rebooting the server.
The utility program is packaged with the Linux RDAC driver. Rescan can be invoked by
either the
hot_add
or the
mppBusRescan
command.
hot_add
is a symbolic link to
mppBusRescan
. There are man pages for both commands. However, the Linux RDAC driver
does not support LUN deletion. You must reboot the server after deleting the mapped
logical drives.