From: Allen, Jack
Sent: Thursday, February 05, 2009 5:03 PM
To: device-mapper development
Subject: RE: Changing SAN vendors
From: Allen, Jack
Sent: Tuesday, February 03, 2009 6:45 PM
To: dm-devel@xxxxxxxxxx
Subject: Changing SAN vendors
Hello:
Our IT
group has decided to switch SAN Vendors. The switch over for a couple of systems
has gone fine, but I have some questions on some things that have
changed.
First a little information on how the switch over is taking place. The old SAN is a EMC CX and the new SAN is a HP XP. The system is connected to a SAN switch which is then connected to both SANs. We shut down the system, and then rezone the switch/SAN to access the XP now instead of the CX. The XP passes through all the I/O request to the CX. When we know the data can be seen correctly, they do some commands that copies the data from the CX to the XP and then the I/O takes place on the XP from that point on. All this works fine.
When only connected to the CX, I had /dev/mapper/mpath1 and /dev/mapper/mpath2. After the reboot and rezoning /dev/mapper/mpath1 and /dev/mapper/mpath2 are gone and /dev/mapper/mpath3 and /dev/mapper/mpath4 are there. LVM finds the Volume Group and all Logical Volumes with no problem.
My question is what do I have to change in some configuration file or what ever to make /dev/mapper/mpath1 and /dev/mapper/mpath2 be in place instead of /dev/mapper/mpath3 and /dev/mapper/mpath4?
I know this is not creating any real problem, but it is kind of misleading, because it looks like 2 paths are missing.
-----
Thanks
Jack
Allen
=================================================================
Well no one replied, so I will answer my on question in hopes that it may help someone else. But I will ask another question and hope someone will reply to it, because I have goggled and can not find the answers.
The Answer: The friendly names are kept in /var/lib/multipath/bindings. Because the WWID changed multipathd created new entries. All I had to do was remove the entries for the old WWID and change the friendly name for the new WWID. Simple, but hard to locate the file when no documents I could find to begin with tells you that is where the friendly names are kept.
The Question: The first system was running RH EL 5.2, but the next system is running RH AS 4.7. There was no /var/lib/multipath directory, therefore no bindings file. So I created both, and entered mpath0 and mpath1 with the WWID, but it still uses mpath2 and mpath3. I know multipathd are different version between the two RH Release. Is there something else I need to change on the RH AS 4.7 system to make it use the mpath0 and mpath1 names?
-----
Thanks:
Jack Allen
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