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Help reconfiguring Powerpath drive order after disaster recovery
Hello, hoping to find some help on steps, file edits required to reconfigure powerpath on RHEL system to make drive order correct again. I'm having trouble locating clear documentation on any of these steps. I watched a lot of experts trying yesterday and not succeeding. I thought this would be much easier but everytime they moved idx and dat files around, edited files, restarted PP, rebooted the drives would just be shuffled in the wrong order or appended, but back to a wrong state again. Seems like this would be a much simpler and easier drive binding scheme to manage and admin. Can anyone lead me to a GOOD document, post or make some helpful comments?
SCENARIO
1. System working fine with half dozen or so luns running on a Clariion from a RHEL 5 system.
2. System backup restored to a duplicate system on remote site. Clariion drives replicated over to identical subsystem on remote site.
3. Remote system booted and sees new drives with NEW WWIDs and simply appends and shuffles the drive order around.
4. Try to fix, edit files, stop start powerpath and always comes back wrong in some way. Need to duplicate the order of drives as they were seen on the old system.
Thanks!
jml9904
64 Posts
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January 25th, 2011 11:00
Suggest using "emcpadm renamepseudo" command followed by "powermt save" to reorder drives as desired.
DougStorage
15 Posts
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January 25th, 2011 12:00
Thanks I missed your reply but have it now. Much appreciated. Any other comments welcome.
DougStorage
15 Posts
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January 25th, 2011 12:00
Follow up post. I'm hoping to gain some knowledge on best practice when moving a system in a DR situation like this. I know multipath software on a host recognizes each lun as a unique device by using the unique WWID/UID or World Wide Name of the disk or SAN lun which gets that number assigned when created on the SAN array. In this case using Navisphere-Unisphere.
First of all the host detects the luns with multiple paths and assigns /etc/sd device to each path, say four per device...
Then the powerpath or mp software-drivers detect those and map the device WWID, it's sd path devices to a single /dev/emcpowerxx device name.
I'm thinking the sd names used for the paths might be able to be different on the old source and new target system but I'm curious if the Host Lun IDs for the clariion luns on the old system have to not only be in the same sequence-order but also be the same exact IDs such as 0,1,2,3,4,5
It also looks like I have to remove luns from a storage group and readd them to reassign the host lun mappings.
If anyone can clarify or set me straight on this scenario it would greatly help.
SKT2
1.3K Posts
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February 13th, 2011 18:00
is it a boot from SAN environment you are trying to bring up on DR side?
Also what did you exactly restore on the DR host and how? I am not clear why the device conflicts arise at the first? what do you need to have a devices in order?