Multipath

Multipathing in Linux is actually composed of 2 parts, the dm_multipath kernel module and the multipathd daemon. The kernel module handles the devices and paths and the daemon monitors the paths and performs failover and grouping.
Proper monitoring requires checking the paths for failures and verifying that multipathd is running. While multipathd will handle single path failures to keep I/O flowing, it does not perform notifications for failures and recoveries. We implemented the check_multipath script to provide notification of path failures and recoveries through NOCpulse.
The current version of the script, available from this page, will look for failed paths and verify that the multipathd daemon is running.

Installation

Download the script to any host using multipath to manage SAN exported from the 3par devices. Edit the /etc/sudoers file using the "visudo" command and make sure this line is present:
Copy the script to /usr/local/bin and make sure it has world read and execute privileges (eg: chmod 0755 /usr/local/bin/check_multipath)
Add a "Remote Program" check in NOCpulse and set the command to "/usr/local/bin/check_multipath" and push the new check to the appropriate scout.

Output

When the script runs, it will output up to 2 status lines. For normal operation, the first line gives the status of the paths and the other line gives the status of the multipathd daemon. The possible status lines are listed below:
MULTIPATH: UNKNOWN - sudo not configured
You did not install the check correctly. Re-read this page.
MULTIPATH: UNKNOWN - /sbin/multipath not found
The Device Mapper Multipath package may not be installed.
MULTIPATH: UNKNOWN - module dm_multipath not loaded
The multipath kernel module is not loaded. Multipath may not be installed.
MULTIPATH: WARNING - no paths defined
Multipath is set up and working but no SAN volume has been exported to the host.
MULTIPATH: OK - no failed paths
MULTIPATH: OK - multipathd running
Everything is ok.
MULTIPATH: OK - no failed paths
MULTIPATH: CRITICAL - multipathd NOT running
The paths are ok but the multipathd daemon is not running. Start it up.
MULTIPATH: CRITICAL - X paths failed
MULTIPATH: OK - multipathd running
At least one of the paths have failed but the multipathd daemon is running. Depending on how many SAN volumes are exported to the host and how many paths are failed, this may be a SAN outage for the host or degraded performance. Log in to the host and check the paths. Escalate appropriately.
MULTIPATH: CRITICAL - X paths failed
MULTIPATH: CRITICAL - multipathd NOT running
At least one of the paths have failed and the multipathd daemon is not running. Depending on how many SAN volumes are exported to the host and how many paths are failed, this may be a SAN outage for the host or degraded performance. Log in to the host, check the paths and start the multipathd daemon.