EMC PowerPath Install

[Youlette Etienne_2]

Hello Everyone,

Last week, we migrated our SAN from a cx600 to a cx700, with EMC onsite. I spent quite a significant amount of time performing the vgexport/vgimport commands for 7 servers since the device path names changed.
Now, we have to install PowerPath, which is new to us. The EMC consultant tells me on Monday that the LUN device file names may change when PowerPath is installed. Of course he was not sure after I questioned for a definite answer. I checked the Powerlink (and the ITRC as well) docs and did not find anything that indicated that the existing device file names will change, only that I should remove the alternate pvlink, but these were the installation guides. I do not see a reason for the device file names to change, but I am new to this product. Can I get a definite answer from the Sys Admins here who have installed powerpath on an existing server? For rp7410, rp7420, and n-class servers.

thanks

[Mauro Gatti · Accepted solution]

Hello Etienne,
as far as I know powerpath doesn't change device file.
The main difference is you haven't to configure alternate link (PV link) because powerpath automatically knows which are alternate paths even if they aren't specified in VG configuration.
I deal with L,N,K,D and A class and a CX700 storage system.
Let me know if you find out any other powerpath behaviour.

Regards

[Youlette Etienne_2]

thanks, that is much more reassuring. I was quite amazed that the EMC consultant did not know for sure. From what I've read so far, it provides I/O load balancing as well. Not having to configure the pvlinks anymore does make things a bit easier.

[Mauro Gatti]

check also correct failover policy that would be "policy=CLAROpt" (check it using "powermt display dev=all" command and check it for each clariion LUN)

Bye

[Youlette Etienne_2]

Also, for each initiated host, under teh connectivity status, on the SPs, should the failover mode remain set to "1" after powerpath is installed?

[Mauro Gatti]

This is the most difficult question because EMC technics too about failover mode settings are not so sure :-)
As far as I know if you use powerpath you would have to use failover setup wizard to set all hosts with initietor type "Clariion Open" and failover mode "0"

[Youlette Etienne_2]

Thanks. I think EMC mentioned the same "0" setting, but after this powerpath issue, I was not too confident about that answer either.

[Stuart Abramson]

1. PowerPath doesn't change device file names. The EMC guy should have known that.
2. the Clariion config for volumes with PowerPath is different than for PVLINKS. There are two variables that change:
Intiator Type
Failover Mode

See the EMC Manual "EMC Host Connectivity Guide for HP-UXâ

[Youlette Etienne_2]

thanks. I will check that manual now.

[Youlette Etienne_2]

information was most helpful