Storage : WWID's recorded in RHEV database - why ?

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Hi

What is the reason for storing the WWID's of the luns that make up a fibre channel based storage domain in the RHEV database?   Is it purely so the manager knows which luns have been allocated and is able to identify newly added luns ?

The reason for my question is that if WWID's were not recorded it would allow customers to use replicated storage solutions for disaster recover/business continuity purposes. As it stands, the WWID's of the replicated luns would not match what is recorded in the database and I'm pretty sure RHEV manager would flag as an issue. (Worse still, it might identify the luns as "new" and possibly allow the user to add luns to a storage domain that are in fact already in use with existing PV's.)

I am refering to field "lun_id" in the "luns" table in the RHEV DB.

Thanks

Richard Davis's picture
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DY Guru 5340 points
14 January 2013 4:19 PM

The WWIDs are used for mapping LUNs to parts of storage domains. You can mask them if you have to, by using user-friendly-names and aliases in multipath.conf

Richard Davis's picture Guru 2354 points
15 January 2013 11:11 AM

Thanks Dan.  I'll give it a go on our test environment.

I assume user_friendly_names would have to be configured on the hypervisors before we create the storage domains , otherwise the WWID's would have already been recorded in the RHEV DB ? 

Since we use the "blackbox" version of the hypervisor, would changing to user_friendly_names still be supported ?  Would it get overwritten upon upgrade of the hypervisor ?

Richard Davis's picture Guru 2354 points
22 January 2013 10:49 AM

Dan, thanks for that.

I've been able to configure my test environment to use "user_friendly_names" as per the knowledge base article and can see that the names are reflected in the RHEV DB as oppossed to their WWID's.   Great!   I'll have a go at replicating the lun and see what happens. 

Are we allowed to make changes to multipath.conf on a blackbox type hypervisor and still expect RH to support it?    

I'm not expecting you to commit an answer to this.   I raise a support call for clarification.

 

Thanks again for all you help.

pa Expert 917 points
23 May 2013 8:23 AM

Richard,

I also need to modify multipath.conf.
Did you get an answer if it's supported or not?

Sadique Puthen's picture Red Hat Guru 4649 points
23 May 2013 10:55 AM

In general, any kind of modifications to hypervisors via shell is not supported if done without involving support first.

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