Tag Archives: PowerPath

EMC PowerPath Internal Error Migrations May Be Pending Fix

A host side migration between arrays can be a nerve racking task especially when you come across issues. Data loss is a constant fear in the back of your mind and what is your fail-back plan should you need to execute it. During a PowerPath migration, I learned the hard way that a host side copy of the boot-from-san lun is NOT supported. After setting up the migration and upon the sync command the Windows machine froze to a halt until it went offline.

After troubleshooting it was clear that the EMC PowerPath Migration Enabler Service needed to be disabled for the Windows machine to fully boot. After enabling EMC PowerPath Migration Enabler after the host was booted would immediately cause the Windows host to go unresponsive and hard power cycle was the only fix.

I could not start the PowerPath Migration Enabler service to abort the session since it would immediately freeze the server and secondly I was unable to uninstall PowerPath Migration Enabler since there was a session pending. I was in a pickle!

EMC PowerPath PPME Removal Migration Pending

After a support ticket with EMC, the resolution requires you to manually remove the PowerPath Migration Enabler database and keys within the registry. After preforming a few deletions then you will be able to star the service successfully without freezing your server and with no active sessions going.

  1. Delete the UMD by deleting the files from C:\Program Files\EMC\PPME\db*.* 
  2. Delete the all subkeys with Prefix “dm_” EXCEPT for dev_conf under, HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\EmcPowerPath\KMD_*.
    The Keys would be dm_ac, dm_control_io_to_clones, dm_funnel_io, dm_wc.EMC PowerPath PPME Removal Migration Pending_Registry
  3. Reboot.

 

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EMC PowerPath Multipathing in RedHat Linux Guide

First and foremost, I want to give the credit to Will’s Notes for the original article on Multipathing in RHEL5. I was able to use this guide with a Xiotech SAN to configure Multipathing. EMC makes it a ton easier to configure Multipathing. EMC has a product called PowerPath, PowerPath can be used with or without a license. If you install and use PowerPath in an unlicensed fashion you have an active-passive connection back to the EMC SAN. If PowerPath is licensed, this allows for an active-active connection back to the EMC SAN. Active-active is not only highly available it is load balanced.

Configuring PowerPath was rather easy to my surprise. Download PowerPath from powerlink.emc.com for your correct distribution and install the RPM.

[root@localhost ~]# rpm -iv EMCPower.LINUX-5.6.0.00.00-143.RHEL5.x86_64.rpm

If you are using PowerPath in licensed mode, register license key with the first command and check the registration of PowerPath with the second command listed below.

[root@localhost ~]# emcpreg -install
[root@localhost ~]# powermt check_registration

Once PowerPath is installed you can rescan the bus or if you do not know how simply reboot RHEL.

To view the information about PowerPath issue the following command.

[root@localhost ~]# powermt display dev=all
Pseudo name=emcpowera
CLARiiON ID=<SERIALNUMBER> [STROAGEGROUP_NAME]
Logical device ID=STORAGEGROUP_WWN [LUN 400]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0;
Owner: default=SP B, current=SP B       Array failover mode: 4
==============================================================================
--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---
###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors
==============================================================================
3 qla2xxx                  sdb       SP A0     unlic   alive       0      0
3 qla2xxx                  sdd       SP B0     unlic   alive       0      0
3 qla2xxx                  sdf       SP A4     active  alive       0      0
3 qla2xxx                  sdh       SP B4     active  alive       0      0
4 qla2xxx                  sdj       SP A1     unlic   alive       0      0
4 qla2xxx                  sdl       SP B1     unlic   alive       0      0
4 qla2xxx                  sdn       SP A5     unlic   alive       0      0
4 qla2xxx                  sdp       SP B5     unlic   alive       0      0

Pseudo name=emcpowerb
CLARiiON ID=<SERIALNUMBER> [STROAGEGROUP_NAME]
Logical device ID=STORAGEGROUP_WWN [LUN 401]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0;
Owner: default=SP A, current=SP A       Array failover mode: 4
==============================================================================
--------------- Host ---------------   - Stor -   -- I/O Path --  -- Stats ---
###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors
==============================================================================
3 qla2xxx                  sdc       SP A0     unlic   alive       0      0
3 qla2xxx                  sde       SP B0     unlic   alive       0      0
3 qla2xxx                  sdg       SP A4     active  alive       0      0
3 qla2xxx                  sdi       SP B4     active  alive       0      0
4 qla2xxx                  sdk       SP A1     unlic   alive       0      0
4 qla2xxx                  sdm       SP B1     unlic   alive       0      0
4 qla2xxx                  sdo       SP A5     unlic   alive       0      0
4 qla2xxx                  sdq       SP B5     unlic   alive       0      0

Once PowerPath is installed and PowerPath is able to access the LUNs that are presented to the host, begin to create the filesystem. Create the file system like you would format any ordinary storage device but instead of /dev/sda, /dev/sdb, etc… EMC’s PowerPath devices are /dev/emcpowera, /dev/emcpowerb, /dev/emcpowerc, etc..

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