[prev in list] [next in list] [prev in thread] [next in thread] 

List:       redhat-linux-cluster
Subject:    Re: [Linux-cluster] Get qdisk to use /dev/mapper/mpathx devices
From:       "Celso K. Webber" <celsowebber () yahoo ! com>
Date:       2010-05-08 2:43:34
Message-ID: 218667.28100.qm () web111713 ! mail ! gq1 ! yahoo ! com
[Download RAW message or body]

Hello,


----- Original Message ----
From: Charlie Brady <charlieb-linux-cluster@budge.apana.org.au>

> Your qdisk label should be unique, and you should be controlling 
> visibility of qdisks.

I think you did not understand what I meant. If you have multiple devices pointing to \
the same LUN (this happens with many multipathing software), your OS will end up with \
various block devices in /dev pointing to the same LUN, thus making qdiskd to pick up \
the first one it founds, and ignoring the rest. If it not picks the right one, you'll \
have no reason to have multipath connections to your shared storage. So its obvious \
that my disk label is unique, the problem is when you have multiple devices pointing \
to it.

> Another case is when the device is not found at all, this 
> happened to me before.

> > If that happens, you have a bigger problem than just using the qdisk label 
> > to identify the qdisk, don't you?

No, I don't agree. I had a very recent situation with a RHEL 5.3 AP installation, EMC \
CX series storage (Clariion), PowerPath multipathing software, where the qdiskd \
simply didn't recognize the /dev devices associated to the quorum disk LUN. It simply \
didn't initialize because didn't find the label on any device it scanned. Simply \
pointing it to the correct PowerPath pseudo device, /dev/emcpowerq in this case, \
solved the problem.

Again, I'm not discussing specific situations using Linux DM multipathing software, \
but other solutions such as EMC's PowerPath.

And I'm sure I have enough experience with that, working for more than 5 years on \
field implementations for Dell.

My intention was to add experience, for me the best option is ALWAYS to use the \
device you want. Even with Linux DM Multipath devices.

thank you.

Regards, Celso.



      

--
Linux-cluster mailing list
Linux-cluster@redhat.com
https://www.redhat.com/mailman/listinfo/linux-cluster


[prev in list] [next in list] [prev in thread] [next in thread]