Migrer de Multipath à Powerpath sur RedHat

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1 Introduction

Powerpath is the multipathing solution for EMC arrays. The multipath package is so bugged on RedHat that you shouldn't install it in production environnement. This migration has been released on RedHat 4.6.EL.

Reminder : Multipathing bring redudancy functionnalities with 2 links on a disks array without having I/O errors.

2 Uninstalling multipath

Multipath package name (if installed) can be found by that way :

Command rpm
rpm -qa | grep multipath

Next, you just need to bring back the package name and add it to the rpm command :

Command rpm
rpm -e device-mapper-multipath-0.4.5-27.el4_6.3

Now reboot !

3 Installation

Now we'll install the package. Take if from the CD or anywhere else and install it :

Command rpm
rpm -ivh EMCpower.Linux*.rpm

Now you'll need to launch the license key command :

Command emcpreg
emcpreg -install

Now update the initial ramdisk :

Command mkinitrd
mkinitrd -f /boot/initrd-`uname -r`.img `uname -r`

Then reboot again !

4 Powerpath verification

You may need to start Powerpath service :

/etc/init.d/PowerPath start

And also may reboot the server again.
Now enter powermt command to verifiy if your LUN can be shown :

Command powermt
$ powermt display dev=all
Pseudo name=emcpowerb ? All the paths below are handled through this pseudo-device
CLARiiON ID=APM00023500472
Logical device ID=600601F0310A00006F80C3D32D69D711? Unique ID of LUN (LUN Properties)
state=alive; policy=CLAROpt; priority=0; queued-IOs=0? properties/status of the paths
---------------- Host ---------------   - Stor -   -- I/O Path -  -- Stats ---
### HW Path                 I/O Paths    Interf.   Mode    State  Q-IOs Errors
  2 QLogic Fibre Channel 2300 sdc        SP A1     active  alive      0      0
  2 QLogic Fibre Channel 2300 sde        SP B0     active  alive      0      0
  3 QLogic Fibre Channel 2300 sdg        SP B1     active  alive      0      0
  3 QLogic Fibre Channel 2300 sdi        SP A0     active  alive      0      0

You can also check that you have emc devices :

Command ls
$ ls /dev/emcpower*
emcpower emcpowera

5 Configuring LVM

Now all is ok, but you need to recover your previous partitions from LVM. So edit the LVM config file, edit it and add thoses arguments :

Configuration File /etc/lvm/lvm.conf
filter = [ "r/sd*/", "a/.*/", "a|/dev/sdb[1-9]|", "a|/dev/mapper/.*$|", "r|.*|" ]

Now you can reboot or rebuild the LVM cache :

Command vgscan
vgscan -v

Now you should see all your disks :-). Look also the /dev/mapper you'll see them too.