Planning Mpio - IBM System Storage DS3500 Introduction And Implementation Manual

AIX.fm
To implement SAN boot on a new system, you can:
– Start the AIX installation from a bootable AIX CD install package.
– Use the Network Installation Manager (NIM).
The methods known as alt_disk_install or mirroring are simpler to implement than the more
complete and more sophisticated method using the Network Installation Manager (NIM).

21.1.3 Planning MPIO

With Multiple Path I/O (MPIO), a device can be individually detected through one or more
physical connections, or paths. A path-control module (PCM) provides the path management
functions.
Note: At the time of writing this Redbook publication, even though both MPIO and RDAC
were available, RDAC is being replaced by MPIO. So we will only cover the MPIO multipath
driver.
An MPIO-capable device driver can control more than one type of target device. A PCM can
support one or more specific devices. Therefore, one device driver can be interfaced to
multiple PCMs that control the I/O across the paths to each of the target devices. The AIX
PCM has a health-check capability that can be used to do the following:
Check the paths and determine which paths are currently usable for sending I/O.
Enable a path that was previously marked failed because of a temporary path fault (for
example, when a cable to a device was removed and then reconnected).
Check currently unused paths that might used if a failover occurred (for example, when the
algorithm attribute value is failover, the health check can test the alternate paths).
This device driver is packaged with the AIX set of installation media and will automatically be
installed with AIX if the POWER system has HBAs physically on the machine or LPAR when it
was installed. If the HBAs are physically installed afterwards or dynamically associated with
the LPAR then there is a possibility that all License Program Products (LPPs) and
prerequisites for the MPIO (and the HBA device drivers) are not installed. In this case the AIX
installation media might be required when the command cfgmgr is run. The command will
automatically configure the HBAs to AIX and, with the installation media install all the required
HBA and MPIO LPPs. For example, to use the media on device /dev/cd0, insert installation
media CD 1 in the CDROM and enter the command: cfgmgr -i /dev/cd0
You might be prompted to insert another CD media if needed to complete the configuration,
after which you can re-apply the Technology Level (TL) package again, containing updates to
the base level file sets just installed on the CD media. To do this, follow your normal
procedure of applying TL maintenance to AIX.
It is possible to verify that the MPIO driver packages is correctly installed as shown in
Example 21-3.
Example 21-3 Verify that the following packages are installed
# lslpp -al |grep -i mpio
devices.common.IBM.mpio.rte
646
IBM System Storage DS3500: Introduction and Implementation Guide
Draft Document for Review March 28, 2011 12:24 pm
6.1.4.0 COMMITTED MPIO Disk Path Control Module