Hello,

----- Original Message ----
From: Charlie Brady <[email protected]>

> 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.



      

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