EMC PowerPath is a server-resident software solution that enhances performance and information availability. It integrates multiple path I/O capabilities, automatic load balancing, and path failover functions into one comprehensive package for use on open server platforms connected to Symmetrix enterprise storage systems.
If your server has two HBA cards connected to EMC SAN storage device, you can implement load-balancing, and fail-over on the HBA cards using the EMC PowerPath software.
Powermt management utility helps you manage I/O paths from the server to the EMC storage device. In this article, let us discuss how to use powermt command with practical examples.
1. powermt display – Display High Level HBA I/O Paths
powermt display command (without any arguments), displays the available HBAs and their current status. The following examples, shows that there are 2 HBAs connected to the server, both the HBAs are in active condition with 2 I/O path’s each. qla2xxx indicates that it is using the Q-Logic HBA card.
This also indicates that the connected EMC device is CLARiiON, as it displays a value for “CLARiiON logical device count” as 1.
2. powermt display dev=all – Display All Attached LUNs
This is the most frequently used powermt command, which will display all the attached logical devices to the server.
The above indicates that there are two LUNs attached to the dev-server with 4 I/O paths from the server to the SAN storage device.
The above command output indicates the following:
- Pseudo name=emcpowera – The device name that can be used by the server. For example, /dev/emcpowera.
- CLARiiON ID=AAA00000000000 [dev-server] – EMC CLARiiON CX3 serial number and the server name.
- Logical device ID=11111111 [LUN 1] – LUN number. For example, LUN 1.
- state=alive; policy=CLAROpt; – This displays that this particular LUN is valid and using the CLAROpt policy.
- Owner: default=SP B, current=SP B – This indicates that the default (and current) owner for this LUN is storage processor SP B.
3. powermt display dev=emcpowera – Display specific LUN
When there are multiple LUNs connected to a server, you might want to view information about a specific LUN by providing the logical name of the LUN as shown below.
If the device is not available, you’ll get a “Bad dev value” as shown below.
4. powermt check_registration – Display PowerPath Registration Key / Status
If you’ve lost the PowerPath registration key that you’ve used during the EMC PowerPath installation, you can retrieve it using the following command.
5. powermt display options – Display EMC PowerPath Options
Displays the high level EMC SAN array options as shown below.
6. powermt display hba_mode – Display PowerPath HBA Mode
This is similar to #1, but displays whether hba is enabled or not, as shown in the last column of the output.
7. powermt display path – Display available I/O Paths.
This displays all available path for your SAN device.
8. powermt displays port_mode – Display Port Status
Displays the status of the individual ports on the HBA. i.e Whether the port is enabled or not.
9. powermt version – Display EMC PowerPath Version
How to identify the version number of EMC PowerPath software?
10. powermt check – Check the I/O Paths
If you have made changes to the HBA’s, or I/O paths, just execute powermt check, to take appropriate action. For example, if you have manually removed an I/O path, check command will detect a dead path and remove it from the EMC path list.
Note: If you want powermt to automatically remove all dead paths, without any confirmation, execute “powermt check force”.
11. powermt set mode hba – Forcefully set the mode for a specific HBA
You can change the mode of a specific HBA to either standby or active using this command. Following example, changes HBA #1’s mode from active to standby.
After the above command, you can see the mode for HBA#1 changed to standby, as shown below.
Note: Path mode can also be “unlic” indicating that you’ve not registered the PowerPath with proper License key.
Note: Some powermt commands (for example, powermt set port_disable), is restricted to certain platform and storage type — On AIX and Solaris, only Fibre channel is supported. On HP-UX, only iSCSI and Fibre are supported. On Linux, Only iSCSI (HBAs) and Fibre are supported.
12. powermt remove – Delete an I/O Path
Use this command to remove any specific I/O path (or) a whole device.
The following example has 4 I/O Paths.
To remove I/O Path sdd, execute the following powermt remove command.
Following will remove all I/O Path for a particular device. i.e To remove /dev/emcpowera, do the following. If the /dev/emcpowera is mounted and used by some program, following command will not work.
13. powermt config – Configure PowerPath
This command checks for available EMC SAN logical devices and add those to PowerPath configuration list. Powermt config command, sets some of the options to it’s default values. For example, write throttling = off, HBA mode = active, CLARiiON policy = CLAROpt, etc.
Possible EMC SAN LUN policy values are: Adaptive, BasicFailover, CLAROpt, LeastBlocks, LeastIos, NoRedirect, Request, RoundRobin, StreamIO, or SymmOpt.
After you execute the powermt config, if you don’t like any of the default values, you should change it accordingly.
14. powermt restore – Make Dead I/O Path Alive
If you have dead I/O paths, and if you’ve done something to fix the issue, you can request PowerPath to re-check the paths and mark it as active using powermt restore command.
When you execute powermt restore, it does an I/O path check. If a previously dead path is alive, it will be marked as alive, and if a previously alive path is dead, it will be marked as dead.
For some reason, if you see the default owner and the current owner of a particular LUN is not the same storage processor, then execute the following command, which will make the current owner of the LUN same as the default owner.
Instead of dev, you can also specify class in the powermt restore command. Class can be one of the following depending on your system.
- symm – Symmetrix
- clariion – CLARiiON
- invista – Invista
- ess – IBM ESS
- hitachi – Hitachi Lightning TagmaStore
- hpxp – HP StorageWorks XP, or EVA series
- hphsx – HP StorageWorks EMA, or MA
- all – All systems
15. Powermt Save and Load – Save and Restore PowerPath Configurations
powermt save – Save the current Powerpath Configuration
If you are changing the PowerPath configurations for testing purpose, you can save the current configuration using powermt save command.
Use this method to backup the current PowerPath Configurations.
This will save the current powermt configuration to /etc/powermt.custom file. Following is the partial content of this file.
If you want to store the current PowePath configuration to a different file, do the following.
powermt load – Load a previously saved EMC PowerPath Configuration
Powerpath License Price
When you are testing EMC PowerPath configuration, if you are not satisfied with the new configuration, you can go back to the previous configuration.
Powerpath License Cost
For example, to restore the configuration to a specific file that you created in the above powermt save example, do the following.