Topics: EMC, Installation, SAN, Storage

EMC and MPIO

You can run into an issue with EMC storage on AIX systems using MPIO (No Powerpath) for your boot disks:

After installing the ODM_DEFINITONS of EMC Symmetrix on your client system, the system won't boot any more and will hang with LED 554 (unable to find boot disk).

The boot hang (LED 554) is not caused by the EMC ODM package itself, but by the boot process not detecting a path to the boot disk if the first MPIO path does not corresponding to the fscsiX driver instance where all hdisks are configured. Let me explain that more in detail:

Let's say we have an AIX system with four HBAs configured in the following order:

# lscfg -v | grep fcs
fcs2 (wwn 71ca) -> no devices configured behind this fscsi2 driver instance (path only configured in CuPath ODM table)
fcs3 (wwn 71cb) -> no devices configured behind this fscsi3 driver instance (path only configured in CuPath ODM table)
fcs0 (wwn 71e4) -> no devices configured behind this fscsi0 driver instance (path only configured in CuPath ODM table)
fcs1 (wwn 71e5) -> ALL devices configured behind this fscsi1 driver instance
Looking at the MPIO path configuration, here is what we have for the rootvg disk:
# lspath -l hdisk2 -H -F"name parent path_id connection status"
name   parent path_id connection                      status
hdisk2 fscsi0 0       5006048452a83987,33000000000000 Enabled
hdisk2 fscsi1 1       5006048c52a83998,33000000000000 Enabled
hdisk2 fscsi2 2       5006048452a83986,33000000000000 Enabled
hdisk2 fscsi3 3       5006048c52a83999,33000000000000 Enabled
The fscsi1 driver instance is the second path (pathid 1), then remove the 3 paths keeping only the path corresponding to fscsi1 :
# rmpath -l hdisk2 -p fscsi0 -d
# rmpath -l hdisk2 -p fscsi2 -d
# rmpath -l hdisk2 -p fscsi3 -d
# lspath -l hdisk2 -H -F"name parent path_id connection status"
Afterwards, do a savebase to update the boot lv hd5. Set up the bootlist to hdisk2 and reboot the host.

It will come up successfully, no more hang LED 554.

When checking the status of the rootvg disk, a new hdisk10 has been configured with the correct ODM definitions as shown below:
# lspv
hdisk10 0003027f7f7ca7e2 rootvg active
# lsdev -Cc disk
hdisk2 Defined   00-09-01 MPIO Other FC SCSI Disk Drive
hdisk10 Available 00-08-01 EMC Symmetrix FCP MPIO Raid6
To summarize, it is recommended to setup ONLY ONE path when installing an AIX to a SAN disk, then install the EMC ODM package then reboot the host and only after that is complete, add the other paths. Dy doing that we ensure that the fscsiX driver instance used for the boot process has the hdisk configured behind.



If you found this useful, here's more on the same topic(s) in our blog:


UNIX Health Check delivers software to scan Linux and AIX systems for potential issues. Run our software on your system, and receive a report in just a few minutes. UNIX Health Check is an automated check list. It will report on perfomance, capacity, stability and security issues. It will alert on configurations that can be improved per best practices, or items that should be improved per audit guidelines. A report will be generated in the format you wish, and the report includes the issues discovered and information on how to solve the issues as well.

Interested in learning more?